Merge branch 'master' into usernam3-sample-clause-links-fix

contrib/boost

@@ -1 +1 @@
-Subproject commit 8fe7b3326ef482ee6ecdf5a4f698f2b8c2780f98
+Subproject commit aec12eea7fc762721ae16943d1361340c66c9c17

docs/en/engines/table-engines/special/distributed.md

@@ -258,4 +258,4 @@ Since [remote](../../../sql-reference/table-functions/remote.md) and [cluster](.
 
 - [Virtual columns](../../../engines/table-engines/index.md#table_engines-virtual_columns) description
 - [background_distributed_schedule_pool_size](../../../operations/settings/settings.md#background_distributed_schedule_pool_size) setting
-- [shardNum()](../../../sql-reference/functions/other-functions.md#shard-num) and [shardCount()](../../../sql-reference/functions/other-functions.md#shard-count) functions
+- [shardNum()](../../../sql-reference/functions/other-functions.md#shardnum) and [shardCount()](../../../sql-reference/functions/other-functions.md#shardcount) functions

docs/en/operations/named-collections.md

@@ -167,9 +167,9 @@ user = 'myuser',
 password = 'mypass',
 host = '127.0.0.1',
 port = 3306,
-database = 'test'
-connection_pool_size = 8
-on_duplicate_clause = 1
+database = 'test',
+connection_pool_size = 8,
+on_duplicate_clause = 1,
 replace_query = 1
 ```
 

docs/en/operations/server-configuration-parameters/settings.md

@@ -917,9 +917,9 @@ We recommend using this option in macOS since the `getrlimit()` function returns
 
 Restriction on deleting tables.
 
-If the size of a [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table exceeds `max_table_size_to_drop` (in bytes), you can’t delete it using a DROP query.
+If the size of a [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table exceeds `max_table_size_to_drop` (in bytes), you can’t delete it using a [DROP](../../sql-reference/statements/drop.md) query or [TRUNCATE](../../sql-reference/statements/truncate.md) query.
 
-If you still need to delete the table without restarting the ClickHouse server, create the `<clickhouse-path>/flags/force_drop_table` file and run the DROP query.
+This setting does not require a restart of the Clickhouse server to apply. Another way to disable the restriction is to create the `<clickhouse-path>/flags/force_drop_table` file.
 
 Default value: 50 GB.
 
@@ -931,6 +931,28 @@ The value 0 means that you can delete all tables without any restrictions.
 <max_table_size_to_drop>0</max_table_size_to_drop>
 ```
 
+## max_partition_size_to_drop {#max-partition-size-to-drop}
+
+Restriction on dropping partitions.
+
+If the size of a [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table exceeds `max_partition_size_to_drop` (in bytes), you can’t drop a partition using a [DROP PARTITION](../../sql-reference/statements/alter/partition.md#drop-partitionpart) query.
+
+This setting does not require a restart of the Clickhouse server to apply. Another way to disable the restriction is to create the `<clickhouse-path>/flags/force_drop_table` file.
+
+Default value: 50 GB.
+
+The value 0 means that you can drop partitions without any restrictions.
+
+:::note
+This limitation does not restrict drop table and truncate table, see [max_table_size_to_drop](#max-table-size-to-drop)
+:::
+
+**Example**
+
+``` xml
+<max_partition_size_to_drop>0</max_partition_size_to_drop>
+```
+
 ## max_thread_pool_size {#max-thread-pool-size}
 
 ClickHouse uses threads from the Global Thread pool to process queries. If there is no idle thread to process a query, then a new thread is created in the pool. `max_thread_pool_size` limits the maximum number of threads in the pool.

docs/en/operations/system-tables/build_options.md

@@ -0,0 +1,27 @@
+---
+slug: /en/operations/system-tables/build_options
+---
+# build_options
+
+Contains information about the ClickHouse server's build options.
+
+Columns:
+
+- `name` (String) — Name of the build option, e.g. `USE_ODBC`
+- `value` (String) — Value of the build option, e.g. `1`
+
+**Example**
+
+``` sql
+SELECT * FROM system.build_options LIMIT 5
+```
+
+``` text
+┌─name─────────────┬─value─┐
+│ USE_BROTLI       │ 1     │
+│ USE_BZIP2        │ 1     │
+│ USE_CAPNP        │ 1     │
+│ USE_CASSANDRA    │ 1     │
+│ USE_DATASKETCHES │ 1     │
+└──────────────────┴───────┘
+```

docs/en/sql-reference/functions/string-functions.md

@@ -323,11 +323,11 @@ Alias: `REPEAT`
 **Arguments**
 
 - `s` — The string to repeat. [String](../../sql-reference/data-types/string.md).
-- `n` — The number of times to repeat the string. [UInt or Int](../../sql-reference/data-types/int-uint.md).
+- `n` — The number of times to repeat the string. [UInt* or Int*](../../sql-reference/data-types/int-uint.md).
 
 **Returned value**
 
-The single string containing string `s` repeated `n` times. If `n` \< 1, the function returns empty string.
+A string containing string `s` repeated `n` times. If `n` <= 0, the function returns the empty string.
 
 Type: `String`.
 
@@ -345,6 +345,44 @@ Result:
 └────────────────────────────────┘
 ```
 
+## space
+
+Concatenates a space (` `) as many times with itself as specified.
+
+**Syntax**
+
+``` sql
+space(n)
+```
+
+Alias: `SPACE`.
+
+**Arguments**
+
+- `n` — The number of times to repeat the space. [UInt* or Int*](../../sql-reference/data-types/int-uint.md).
+
+**Returned value**
+
+The string containing string ` ` repeated `n` times. If `n` <= 0, the function returns the empty string.
+
+Type: `String`.
+
+**Example**
+
+Query:
+
+``` sql
+SELECT space(3);
+```
+
+Result:
+
+``` text
+┌─space(3) ────┐
+│              │
+└──────────────┘
+```
+
 ## reverse
 
 Reverses the sequence of bytes in a string.

docs/en/sql-reference/statements/select/order-by.md

@@ -547,7 +547,7 @@ Result:
 ## Filling grouped by sorting prefix
 
 It can be useful to fill rows which have the same values in particular columns independently, - a good example is filling missing values in time series.
-Assume there is the following time series table
+Assume there is the following time series table:
 ``` sql
 CREATE TABLE timeseries
 (
@@ -567,7 +567,7 @@ SELECT * FROM timeseries;
 └───────────┴─────────────────────────┴───────┘
 ```
 And we'd like to fill missing values for each sensor independently with 1 second interval.
-The way to achieve it is to use `sensor_id` column as sorting prefix for filling column `timestamp`
+The way to achieve it is to use `sensor_id` column as sorting prefix for filling column `timestamp`:
 ```
 SELECT *
 FROM timeseries
@@ -589,7 +589,7 @@ INTERPOLATE ( value AS 9999 )
 │       432 │ 2021-12-01 00:00:05.000 │     5 │
 └───────────┴─────────────────────────┴───────┘
 ```
-Here, the `value` column was interpolated with `9999` just to make filled rows more noticeable
+Here, the `value` column was interpolated with `9999` just to make filled rows more noticeable.
 This behavior is controlled by setting `use_with_fill_by_sorting_prefix` (enabled by default)
 
 ## Related content

src/Backups/BackupEntryFromImmutableFile.cpp

@@ -58,18 +58,33 @@ UInt64 BackupEntryFromImmutableFile::getSize() const
 }
 
 UInt128 BackupEntryFromImmutableFile::getChecksum() const
+{
+    {
+        std::lock_guard lock{size_and_checksum_mutex};
+        if (checksum_adjusted)
+            return *checksum;
+
+        if (checksum)
+        {
+            if (copy_encrypted)
+                checksum = combineChecksums(*checksum, disk->getEncryptedFileIV(file_path));
+            checksum_adjusted = true;
+            return *checksum;
+        }
+    }
+
+    auto calculated_checksum = BackupEntryWithChecksumCalculation<IBackupEntry>::getChecksum();
+
     {
         std::lock_guard lock{size_and_checksum_mutex};
         if (!checksum_adjusted)
         {
-        if (!checksum)
-            checksum = BackupEntryWithChecksumCalculation<IBackupEntry>::getChecksum();
-        else if (copy_encrypted)
-            checksum = combineChecksums(*checksum, disk->getEncryptedFileIV(file_path));
+            checksum = calculated_checksum;
             checksum_adjusted = true;
         }
         return *checksum;
     }
+}
 
 std::optional<UInt128> BackupEntryFromImmutableFile::getPartialChecksum(size_t prefix_length) const
 {

src/Backups/BackupEntryFromImmutableFile.h

@@ -44,7 +44,7 @@ private:
     const DataSourceDescription data_source_description;
     const bool copy_encrypted;
     mutable std::optional<UInt64> file_size;
-    mutable std::optional<UInt64> checksum;
+    mutable std::optional<UInt128> checksum;
     mutable bool file_size_adjusted = false;
     mutable bool checksum_adjusted = false;
     mutable std::mutex size_and_checksum_mutex;

src/Backups/BackupEntryWithChecksumCalculation.cpp

@@ -7,17 +7,34 @@ namespace DB
 
 template <typename Base>
 UInt128 BackupEntryWithChecksumCalculation<Base>::getChecksum() const
+{
+    {
+        std::lock_guard lock{checksum_calculation_mutex};
+        if (calculated_checksum)
+            return *calculated_checksum;
+    }
+
+    size_t size = this->getSize();
+
     {
         std::lock_guard lock{checksum_calculation_mutex};
         if (!calculated_checksum)
         {
-        auto read_buffer = this->getReadBuffer(ReadSettings{}.adjustBufferSize(this->getSize()));
+            if (size == 0)
+            {
+                calculated_checksum = 0;
+            }
+            else
+            {
+                auto read_buffer = this->getReadBuffer(ReadSettings{}.adjustBufferSize(size));
                 HashingReadBuffer hashing_read_buffer(*read_buffer);
                 hashing_read_buffer.ignoreAll();
                 calculated_checksum = hashing_read_buffer.getHash();
             }
+        }
         return *calculated_checksum;
     }
+}
 
 template <typename Base>
 std::optional<UInt128> BackupEntryWithChecksumCalculation<Base>::getPartialChecksum(size_t prefix_length) const

src/Backups/tests/gtest_backup_entries.cpp

@@ -0,0 +1,350 @@
+#include <gtest/gtest.h>
+
+#include <Backups/BackupEntryFromAppendOnlyFile.h>
+#include <Backups/BackupEntryFromImmutableFile.h>
+#include <Backups/BackupEntryFromSmallFile.h>
+
+#include <Disks/IDisk.h>
+#include <Disks/DiskLocal.h>
+#include <Disks/DiskEncrypted.h>
+#include <IO/FileEncryptionCommon.h>
+#include <IO/ReadHelpers.h>
+#include <IO/WriteHelpers.h>
+
+#include <Poco/TemporaryFile.h>
+
+using namespace DB;
+
+
+class BackupEntriesTest : public ::testing::Test
+{
+protected:
+    void SetUp() override
+    {
+        /// Make local disk.
+        temp_dir = std::make_unique<Poco::TemporaryFile>();
+        temp_dir->createDirectories();
+        local_disk = std::make_shared<DiskLocal>("local_disk", temp_dir->path() + "/", 0);
+
+        /// Make encrypted disk.
+        auto settings = std::make_unique<DiskEncryptedSettings>();
+        settings->wrapped_disk = local_disk;
+        settings->current_algorithm = FileEncryption::Algorithm::AES_128_CTR;
+        settings->keys[0] = "1234567890123456";
+        settings->current_key_id = 0;
+        settings->disk_path = "encrypted/";
+        encrypted_disk = std::make_shared<DiskEncrypted>("encrypted_disk", std::move(settings), true);
+    }
+
+    void TearDown() override
+    {
+        encrypted_disk.reset();
+        local_disk.reset();
+    }
+
+    static void writeFile(DiskPtr disk, const String & filepath)
+    {
+        auto buf = disk->writeFile(filepath, DBMS_DEFAULT_BUFFER_SIZE, WriteMode::Rewrite, {});
+        writeString(std::string_view{"Some text"}, *buf);
+        buf->finalize();
+    }
+
+    static void writeEmptyFile(DiskPtr disk, const String & filepath)
+    {
+        auto buf = disk->writeFile(filepath, DBMS_DEFAULT_BUFFER_SIZE, WriteMode::Rewrite, {});
+        buf->finalize();
+    }
+
+    static void appendFile(DiskPtr disk, const String & filepath)
+    {
+        auto buf = disk->writeFile(filepath, DBMS_DEFAULT_BUFFER_SIZE, WriteMode::Append, {});
+        writeString(std::string_view{"Appended"}, *buf);
+        buf->finalize();
+    }
+
+    static String getChecksum(const BackupEntryPtr & backup_entry)
+    {
+        return getHexUIntUppercase(backup_entry->getChecksum());
+    }
+
+    static const constexpr std::string_view NO_CHECKSUM = "no checksum";
+
+    static String getPartialChecksum(const BackupEntryPtr & backup_entry, size_t prefix_length)
+    {
+        auto partial_checksum = backup_entry->getPartialChecksum(prefix_length);
+        if (!partial_checksum)
+            return String{NO_CHECKSUM};
+        return getHexUIntUppercase(*partial_checksum);
+    }
+
+    static String readAll(const BackupEntryPtr & backup_entry)
+    {
+        auto in = backup_entry->getReadBuffer({});
+        String str;
+        readStringUntilEOF(str, *in);
+        return str;
+    }
+
+    std::unique_ptr<Poco::TemporaryFile> temp_dir;
+    std::shared_ptr<DiskLocal> local_disk;
+    std::shared_ptr<DiskEncrypted> encrypted_disk;
+};
+
+
+static const constexpr std::string_view ZERO_CHECKSUM = "00000000000000000000000000000000";
+
+static const constexpr std::string_view SOME_TEXT_CHECKSUM = "28B5529750AC210952FFD366774363ED";
+static const constexpr std::string_view S_CHECKSUM = "C27395C39AFB5557BFE47661CC9EB86C";
+static const constexpr std::string_view SOME_TEX_CHECKSUM = "D00D9BE8D87919A165F14EDD31088A0E";
+static const constexpr std::string_view SOME_TEXT_APPENDED_CHECKSUM = "5A1F10F638DC7A226231F3FD927D1726";
+
+static const constexpr std::string_view PRECALCULATED_CHECKSUM = "1122334455667788AABBCCDDAABBCCDD";
+static const constexpr UInt128 PRECALCULATED_CHECKSUM_UINT128 = (UInt128(0x1122334455667788) << 64) | 0xAABBCCDDAABBCCDD;
+static const size_t PRECALCULATED_SIZE = 123;
+
+TEST_F(BackupEntriesTest, BackupEntryFromImmutableFile)
+{
+    writeFile(local_disk, "a.txt");
+
+    auto entry = std::make_shared<BackupEntryFromImmutableFile>(local_disk, "a.txt");
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1), NO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 8), NO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 9), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1000), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+
+    writeEmptyFile(local_disk, "empty.txt");
+
+    auto empty_entry = std::make_shared<BackupEntryFromImmutableFile>(local_disk, "empty.txt");
+    EXPECT_EQ(empty_entry->getSize(), 0);
+    EXPECT_EQ(getChecksum(empty_entry), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1000), ZERO_CHECKSUM);
+    EXPECT_EQ(readAll(empty_entry), "");
+
+    auto precalculated_entry = std::make_shared<BackupEntryFromImmutableFile>(local_disk, "a.txt", false, PRECALCULATED_SIZE, PRECALCULATED_CHECKSUM_UINT128);
+    EXPECT_EQ(precalculated_entry->getSize(), PRECALCULATED_SIZE);
+
+    EXPECT_EQ(getChecksum(precalculated_entry), PRECALCULATED_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(precalculated_entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(precalculated_entry, 1), NO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(precalculated_entry, PRECALCULATED_SIZE - 1), NO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(precalculated_entry, PRECALCULATED_SIZE), PRECALCULATED_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(precalculated_entry, 1000), PRECALCULATED_CHECKSUM);
+    EXPECT_EQ(readAll(precalculated_entry), "Some text");
+}
+
+TEST_F(BackupEntriesTest, BackupEntryFromAppendOnlyFile)
+{
+    writeFile(local_disk, "a.txt");
+
+    auto entry = std::make_shared<BackupEntryFromAppendOnlyFile>(local_disk, "a.txt");
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1), S_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 8), SOME_TEX_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 9), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1000), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+
+    appendFile(local_disk, "a.txt");
+
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1), S_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 8), SOME_TEX_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 9), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1000), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+
+    auto appended_entry = std::make_shared<BackupEntryFromAppendOnlyFile>(local_disk, "a.txt");
+    EXPECT_EQ(appended_entry->getSize(), 17);
+    EXPECT_EQ(getChecksum(appended_entry), SOME_TEXT_APPENDED_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 1), S_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 8), SOME_TEX_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 9), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 22), SOME_TEXT_APPENDED_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(appended_entry, 1000), SOME_TEXT_APPENDED_CHECKSUM);
+    EXPECT_EQ(readAll(appended_entry), "Some textAppended");
+
+    writeEmptyFile(local_disk, "empty_appended.txt");
+
+    auto empty_entry = std::make_shared<BackupEntryFromAppendOnlyFile>(local_disk, "empty_appended.txt");
+    EXPECT_EQ(empty_entry->getSize(), 0);
+    EXPECT_EQ(getChecksum(empty_entry), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1000), ZERO_CHECKSUM);
+    EXPECT_EQ(readAll(empty_entry), "");
+
+    appendFile(local_disk, "empty_appended.txt");
+    EXPECT_EQ(empty_entry->getSize(), 0);
+    EXPECT_EQ(getChecksum(empty_entry), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(empty_entry, 1000), ZERO_CHECKSUM);
+    EXPECT_EQ(readAll(empty_entry), "");
+}
+
+TEST_F(BackupEntriesTest, PartialChecksumBeforeFullChecksum)
+{
+    writeFile(local_disk, "a.txt");
+
+    auto entry = std::make_shared<BackupEntryFromAppendOnlyFile>(local_disk, "a.txt");
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+
+    entry = std::make_shared<BackupEntryFromAppendOnlyFile>(local_disk, "a.txt");
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getPartialChecksum(entry, 1), S_CHECKSUM);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+}
+
+TEST_F(BackupEntriesTest, BackupEntryFromSmallFile)
+{
+    writeFile(local_disk, "a.txt");
+    auto entry = std::make_shared<BackupEntryFromSmallFile>(local_disk, "a.txt");
+
+    local_disk->removeFile("a.txt");
+
+    EXPECT_EQ(entry->getSize(), 9);
+    EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1), S_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 8), SOME_TEX_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 9), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(getPartialChecksum(entry, 1000), SOME_TEXT_CHECKSUM);
+    EXPECT_EQ(readAll(entry), "Some text");
+}
+
+TEST_F(BackupEntriesTest, DecryptedEntriesFromEncryptedDisk)
+{
+    {
+        writeFile(encrypted_disk, "a.txt");
+        std::pair<BackupEntryPtr, bool /* partial_checksum_allowed */> test_cases[]
+            = {{std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "a.txt"), false},
+               {std::make_shared<BackupEntryFromAppendOnlyFile>(encrypted_disk, "a.txt"), true},
+               {std::make_shared<BackupEntryFromSmallFile>(encrypted_disk, "a.txt"), true}};
+        for (const auto & [entry, partial_checksum_allowed] : test_cases)
+        {
+            EXPECT_EQ(entry->getSize(), 9);
+            EXPECT_EQ(getChecksum(entry), SOME_TEXT_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 1), partial_checksum_allowed ? S_CHECKSUM : NO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 8), partial_checksum_allowed ? SOME_TEX_CHECKSUM : NO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 9), SOME_TEXT_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 1000), SOME_TEXT_CHECKSUM);
+            EXPECT_EQ(readAll(entry), "Some text");
+        }
+    }
+
+    {
+        writeEmptyFile(encrypted_disk, "empty.txt");
+        BackupEntryPtr entries[]
+            = {std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "empty.txt"),
+               std::make_shared<BackupEntryFromAppendOnlyFile>(encrypted_disk, "empty.txt"),
+               std::make_shared<BackupEntryFromSmallFile>(encrypted_disk, "empty.txt")};
+        for (const auto & entry : entries)
+        {
+            EXPECT_EQ(entry->getSize(), 0);
+            EXPECT_EQ(getChecksum(entry), ZERO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 1), ZERO_CHECKSUM);
+            EXPECT_EQ(readAll(entry), "");
+        }
+    }
+
+    {
+        auto precalculated_entry = std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "a.txt", false, PRECALCULATED_SIZE, PRECALCULATED_CHECKSUM_UINT128);
+        EXPECT_EQ(precalculated_entry->getSize(), PRECALCULATED_SIZE);
+        EXPECT_EQ(getChecksum(precalculated_entry), PRECALCULATED_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 0), ZERO_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 1), NO_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, PRECALCULATED_SIZE), PRECALCULATED_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 1000), PRECALCULATED_CHECKSUM);
+        EXPECT_EQ(readAll(precalculated_entry), "Some text");
+    }
+}
+
+TEST_F(BackupEntriesTest, EncryptedEntriesFromEncryptedDisk)
+{
+    {
+        writeFile(encrypted_disk, "a.txt");
+        BackupEntryPtr entries[]
+            = {std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "a.txt", /* copy_encrypted= */ true),
+               std::make_shared<BackupEntryFromAppendOnlyFile>(encrypted_disk, "a.txt", /* copy_encrypted= */ true),
+               std::make_shared<BackupEntryFromSmallFile>(encrypted_disk, "a.txt", /* copy_encrypted= */ true)};
+
+        auto encrypted_checksum = getChecksum(entries[0]);
+        EXPECT_NE(encrypted_checksum, NO_CHECKSUM);
+        EXPECT_NE(encrypted_checksum, ZERO_CHECKSUM);
+        EXPECT_NE(encrypted_checksum, SOME_TEXT_CHECKSUM);
+
+        auto partial_checksum = getPartialChecksum(entries[1], 9);
+        EXPECT_NE(partial_checksum, NO_CHECKSUM);
+        EXPECT_NE(partial_checksum, ZERO_CHECKSUM);
+        EXPECT_NE(partial_checksum, SOME_TEXT_CHECKSUM);
+        EXPECT_NE(partial_checksum, encrypted_checksum);
+
+        auto encrypted_data = readAll(entries[0]);
+        EXPECT_EQ(encrypted_data.size(), 9 + FileEncryption::Header::kSize);
+
+        for (const auto & entry : entries)
+        {
+            EXPECT_EQ(entry->getSize(), 9 + FileEncryption::Header::kSize);
+            EXPECT_EQ(getChecksum(entry), encrypted_checksum);
+            EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+            auto encrypted_checksum_9 = getPartialChecksum(entry, 9);
+            EXPECT_TRUE(encrypted_checksum_9 == NO_CHECKSUM || encrypted_checksum_9 == partial_checksum);
+            EXPECT_EQ(getPartialChecksum(entry, 9 + FileEncryption::Header::kSize), encrypted_checksum);
+            EXPECT_EQ(getPartialChecksum(entry, 1000), encrypted_checksum);
+            EXPECT_EQ(readAll(entry), encrypted_data);
+        }
+    }
+
+    {
+        writeEmptyFile(encrypted_disk, "empty.txt");
+        BackupEntryPtr entries[]
+            = {std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "empty.txt", /* copy_encrypted= */ true),
+               std::make_shared<BackupEntryFromAppendOnlyFile>(encrypted_disk, "empty.txt", /* copy_encrypted= */ true),
+               std::make_shared<BackupEntryFromSmallFile>(encrypted_disk, "empty.txt", /* copy_encrypted= */ true)};
+        for (const auto & entry : entries)
+        {
+            EXPECT_EQ(entry->getSize(), 0);
+            EXPECT_EQ(getChecksum(entry), ZERO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 0), ZERO_CHECKSUM);
+            EXPECT_EQ(getPartialChecksum(entry, 1), ZERO_CHECKSUM);
+            EXPECT_EQ(readAll(entry), "");
+        }
+    }
+
+    {
+        auto precalculated_entry = std::make_shared<BackupEntryFromImmutableFile>(encrypted_disk, "a.txt", /* copy_encrypted= */ true, PRECALCULATED_SIZE, PRECALCULATED_CHECKSUM_UINT128);
+        EXPECT_EQ(precalculated_entry->getSize(), PRECALCULATED_SIZE + FileEncryption::Header::kSize);
+
+        auto encrypted_checksum = getChecksum(precalculated_entry);
+        EXPECT_NE(encrypted_checksum, NO_CHECKSUM);
+        EXPECT_NE(encrypted_checksum, ZERO_CHECKSUM);
+        EXPECT_NE(encrypted_checksum, SOME_TEXT_CHECKSUM);
+        EXPECT_NE(encrypted_checksum, PRECALCULATED_CHECKSUM);
+
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 0), ZERO_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 1), NO_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, PRECALCULATED_SIZE), NO_CHECKSUM);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, PRECALCULATED_SIZE + FileEncryption::Header::kSize), encrypted_checksum);
+        EXPECT_EQ(getPartialChecksum(precalculated_entry, 1000), encrypted_checksum);
+
+        auto encrypted_data = readAll(precalculated_entry);
+        EXPECT_EQ(encrypted_data.size(), 9 + FileEncryption::Header::kSize);
+    }
+}

src/Common/AsyncLoader.cpp

@@ -6,6 +6,7 @@
 #include <Common/noexcept_scope.h>
 #include <Common/setThreadName.h>
 #include <Common/logger_useful.h>
+#include <Common/ThreadPool.h>
 
 namespace DB
 {
@@ -41,9 +42,14 @@ std::exception_ptr LoadJob::exception() const
     return load_exception;
 }
 
-ssize_t LoadJob::priority() const
+size_t LoadJob::executionPool() const
 {
-    return load_priority;
+    return execution_pool_id;
+}
+
+size_t LoadJob::pool() const
+{
+    return pool_id;
 }
 
 void LoadJob::wait() const
@@ -112,8 +118,9 @@ void LoadJob::enqueued()
         enqueue_time = std::chrono::system_clock::now();
 }
 
-void LoadJob::execute(const LoadJobPtr & self)
+void LoadJob::execute(size_t pool, const LoadJobPtr & self)
 {
+    execution_pool_id = pool;
     start_time = std::chrono::system_clock::now();
     func(self);
 }
@@ -148,22 +155,35 @@ void LoadTask::remove()
     {
         loader.remove(jobs);
         jobs.clear();
+        goal_jobs.clear();
     }
 }
 
 void LoadTask::detach()
 {
     jobs.clear();
+    goal_jobs.clear();
 }
 
-AsyncLoader::AsyncLoader(Metric metric_threads, Metric metric_active_threads, size_t max_threads_, bool log_failures_, bool log_progress_)
+
+AsyncLoader::AsyncLoader(std::vector<PoolInitializer> pool_initializers, bool log_failures_, bool log_progress_)
     : log_failures(log_failures_)
     , log_progress(log_progress_)
     , log(&Poco::Logger::get("AsyncLoader"))
-    , max_threads(max_threads_)
-    , pool(metric_threads, metric_active_threads, max_threads)
 {
-
+    pools.reserve(pool_initializers.size());
+    for (auto && init : pool_initializers)
+        pools.push_back({
+            .name = init.name,
+            .priority = init.priority,
+            .thread_pool = std::make_unique<ThreadPool>(
+                init.metric_threads,
+                init.metric_active_threads,
+                init.max_threads,
+                /* max_free_threads = */ 0,
+                init.max_threads),
+            .max_threads = init.max_threads
+        });
 }
 
 AsyncLoader::~AsyncLoader()
@@ -175,13 +195,20 @@ void AsyncLoader::start()
 {
     std::unique_lock lock{mutex};
     is_running = true;
-    for (size_t i = 0; workers < max_threads && i < ready_queue.size(); i++)
-        spawn(lock);
+    updateCurrentPriorityAndSpawn(lock);
 }
 
 void AsyncLoader::wait()
 {
-    pool.wait();
+    // Because job can create new jobs in other pools we have to recheck in cycle
+    std::unique_lock lock{mutex};
+    while (!scheduled_jobs.empty())
+    {
+        lock.unlock();
+        for (auto & p : pools)
+            p.thread_pool->wait();
+        lock.lock();
+    }
 }
 
 void AsyncLoader::stop()
@@ -191,7 +218,7 @@ void AsyncLoader::stop()
         is_running = false;
         // NOTE: there is no need to notify because workers never wait
     }
-    pool.wait();
+    wait();
 }
 
 void AsyncLoader::schedule(LoadTask & task)
@@ -229,9 +256,9 @@ void AsyncLoader::scheduleImpl(const LoadJobSet & input_jobs)
         old_jobs = finished_jobs.size();
     }
 
-    // Make set of jobs to schedule:
+    // Pass 1. Make set of jobs to schedule:
     // 1) exclude already scheduled or finished jobs
-    // 2) include pending dependencies, that are not yet scheduled
+    // 2) include assigned job dependencies (that are not yet scheduled)
     LoadJobSet jobs;
     for (const auto & job : input_jobs)
         gatherNotScheduled(job, jobs, lock);
@@ -242,17 +269,18 @@ void AsyncLoader::scheduleImpl(const LoadJobSet & input_jobs)
     // We do not want any exception to be throws after this point, because the following code is not exception-safe
     DENY_ALLOCATIONS_IN_SCOPE;
 
-    // Schedule all incoming jobs
+    // Pass 2. Schedule all incoming jobs
     for (const auto & job : jobs)
     {
+        chassert(job->pool() < pools.size());
         NOEXCEPT_SCOPE({
             ALLOW_ALLOCATIONS_IN_SCOPE;
-            scheduled_jobs.emplace(job, Info{.initial_priority = job->load_priority, .priority = job->load_priority});
+            scheduled_jobs.try_emplace(job);
             job->scheduled();
         });
     }
 
-    // Process dependencies on scheduled pending jobs
+    // Pass 3. Process dependencies on scheduled jobs, priority inheritance
     for (const auto & job : jobs)
     {
         Info & info = scheduled_jobs.find(job)->second;
@@ -267,17 +295,18 @@ void AsyncLoader::scheduleImpl(const LoadJobSet & input_jobs)
                 });
                 info.dependencies_left++;
 
-                // Priority inheritance: prioritize deps to have at least given `priority` to avoid priority inversion
-                prioritize(dep, info.priority, lock);
+                // Priority inheritance: prioritize deps to have at least given `pool.priority` to avoid priority inversion
+                prioritize(dep, job->pool_id, lock);
             }
         }
 
         // Enqueue non-blocked jobs (w/o dependencies) to ready queue
-        if (!info.is_blocked())
+        if (!info.isBlocked())
             enqueue(info, job, lock);
     }
 
-    // Process dependencies on other jobs. It is done in a separate pass to facilitate propagation of cancel signals (if any).
+    // Pass 4: Process dependencies on other jobs.
+    // It is done in a separate pass to facilitate cancelling due to already failed dependencies.
     for (const auto & job : jobs)
     {
         if (auto info = scheduled_jobs.find(job); info != scheduled_jobs.end())
@@ -285,12 +314,12 @@ void AsyncLoader::scheduleImpl(const LoadJobSet & input_jobs)
             for (const auto & dep : job->dependencies)
             {
                 if (scheduled_jobs.contains(dep))
-                    continue; // Skip dependencies on scheduled pending jobs (already processed)
+                    continue; // Skip dependencies on scheduled jobs (already processed in pass 3)
                 LoadStatus dep_status = dep->status();
                 if (dep_status == LoadStatus::OK)
                     continue; // Dependency on already successfully finished job -- it's okay.
 
-                // Dependency on not scheduled pending job -- it's bad.
+                // Dependency on assigned job -- it's bad.
                 // Probably, there is an error in `jobs` set, `gatherNotScheduled()` should have fixed it.
                 chassert(dep_status != LoadStatus::PENDING);
 
@@ -305,7 +334,7 @@ void AsyncLoader::scheduleImpl(const LoadJobSet & input_jobs)
                             job->name,
                             getExceptionMessage(dep->exception(), /* with_stacktrace = */ false)));
                     });
-                    finish(lock, job, LoadStatus::CANCELED, e);
+                    finish(job, LoadStatus::CANCELED, e, lock);
                     break; // This job is now finished, stop its dependencies processing
                 }
             }
@@ -327,13 +356,14 @@ void AsyncLoader::gatherNotScheduled(const LoadJobPtr & job, LoadJobSet & jobs,
     }
 }
 
-void AsyncLoader::prioritize(const LoadJobPtr & job, ssize_t new_priority)
+void AsyncLoader::prioritize(const LoadJobPtr & job, size_t new_pool)
 {
     if (!job)
         return;
+    chassert(new_pool < pools.size());
     DENY_ALLOCATIONS_IN_SCOPE;
     std::unique_lock lock{mutex};
-    prioritize(job, new_priority, lock);
+    prioritize(job, new_pool, lock);
 }
 
 void AsyncLoader::remove(const LoadJobSet & jobs)
@@ -347,14 +377,14 @@ void AsyncLoader::remove(const LoadJobSet & jobs)
     {
         if (auto info = scheduled_jobs.find(job); info != scheduled_jobs.end())
         {
-            if (info->second.is_executing())
+            if (info->second.isExecuting())
                 continue; // Skip executing jobs on the first pass
             std::exception_ptr e;
             NOEXCEPT_SCOPE({
                 ALLOW_ALLOCATIONS_IN_SCOPE;
                 e = std::make_exception_ptr(Exception(ErrorCodes::ASYNC_LOAD_CANCELED, "Load job '{}' canceled", job->name));
             });
-            finish(lock, job, LoadStatus::CANCELED, e);
+            finish(job, LoadStatus::CANCELED, e, lock);
         }
     }
     // On the second pass wait for executing jobs to finish
@@ -363,7 +393,7 @@ void AsyncLoader::remove(const LoadJobSet & jobs)
         if (auto info = scheduled_jobs.find(job); info != scheduled_jobs.end())
         {
             // Job is currently executing
-            chassert(info->second.is_executing());
+            chassert(info->second.isExecuting());
             lock.unlock();
             job->waitNoThrow(); // Wait for job to finish
             lock.lock();
@@ -379,25 +409,36 @@ void AsyncLoader::remove(const LoadJobSet & jobs)
     }
 }
 
-void AsyncLoader::setMaxThreads(size_t value)
+void AsyncLoader::setMaxThreads(size_t pool, size_t value)
 {
     std::unique_lock lock{mutex};
-    pool.setMaxThreads(value);
-    pool.setMaxFreeThreads(value);
-    pool.setQueueSize(value);
-    max_threads = value;
+    auto & p = pools[pool];
+    p.thread_pool->setMaxThreads(value);
+    p.thread_pool->setQueueSize(value); // Keep queue size equal max threads count to avoid blocking during spawning
+    p.max_threads = value;
     if (!is_running)
         return;
-    for (size_t i = 0; workers < max_threads && i < ready_queue.size(); i++)
-        spawn(lock);
+    for (size_t i = 0; canSpawnWorker(p, lock) && i < p.ready_queue.size(); i++)
+        spawn(p, lock);
 }
 
-size_t AsyncLoader::getMaxThreads() const
+size_t AsyncLoader::getMaxThreads(size_t pool) const
 {
     std::unique_lock lock{mutex};
-    return max_threads;
+    return pools[pool].max_threads;
 }
 
+const String & AsyncLoader::getPoolName(size_t pool) const
+{
+    return pools[pool].name; // NOTE: lock is not needed because `name` is const and `pools` are immutable
+}
+
+ssize_t AsyncLoader::getPoolPriority(size_t pool) const
+{
+    return pools[pool].priority; // NOTE: lock is not needed because `priority` is const and `pools` are immutable
+}
+
+
 size_t AsyncLoader::getScheduledJobCount() const
 {
     std::unique_lock lock{mutex};
@@ -412,11 +453,10 @@ std::vector<AsyncLoader::JobState> AsyncLoader::getJobStates() const
         states.emplace(job->name, JobState{
             .job = job,
             .dependencies_left = info.dependencies_left,
-            .is_executing = info.is_executing(),
-            .is_blocked = info.is_blocked(),
-            .is_ready = info.is_ready(),
-            .initial_priority = info.initial_priority,
-            .ready_seqno = last_ready_seqno
+            .ready_seqno = info.ready_seqno,
+            .is_blocked = info.isBlocked(),
+            .is_ready = info.isReady(),
+            .is_executing = info.isExecuting()
         });
     for (const auto & job : finished_jobs)
         states.emplace(job->name, JobState{.job = job});
@@ -462,21 +502,21 @@ String AsyncLoader::checkCycleImpl(const LoadJobPtr & job, LoadJobSet & left, Lo
     return {};
 }
 
-void AsyncLoader::finish(std::unique_lock<std::mutex> & lock, const LoadJobPtr & job, LoadStatus status, std::exception_ptr exception_from_job)
+void AsyncLoader::finish(const LoadJobPtr & job, LoadStatus status, std::exception_ptr exception_from_job, std::unique_lock<std::mutex> & lock)
 {
+    chassert(scheduled_jobs.contains(job)); // Job was pending
     if (status == LoadStatus::OK)
     {
         // Notify waiters
         job->ok();
 
         // Update dependent jobs and enqueue if ready
-        chassert(scheduled_jobs.contains(job)); // Job was pending
         for (const auto & dep : scheduled_jobs[job].dependent_jobs)
         {
             chassert(scheduled_jobs.contains(dep)); // All depended jobs must be pending
             Info & dep_info = scheduled_jobs[dep];
             dep_info.dependencies_left--;
-            if (!dep_info.is_blocked())
+            if (!dep_info.isBlocked())
                 enqueue(dep_info, dep, lock);
         }
     }
@@ -488,11 +528,10 @@ void AsyncLoader::finish(std::unique_lock<std::mutex> & lock, const LoadJobPtr &
         else if (status == LoadStatus::CANCELED)
             job->canceled(exception_from_job);
 
-        chassert(scheduled_jobs.contains(job)); // Job was pending
         Info & info = scheduled_jobs[job];
-        if (info.is_ready())
+        if (info.isReady())
         {
-            ready_queue.erase(info.key());
+            pools[job->pool_id].ready_queue.erase(info.ready_seqno);
             info.ready_seqno = 0;
         }
 
@@ -512,7 +551,7 @@ void AsyncLoader::finish(std::unique_lock<std::mutex> & lock, const LoadJobPtr &
                         dep->name,
                         getExceptionMessage(exception_from_job, /* with_stacktrace = */ false)));
             });
-            finish(lock, dep, LoadStatus::CANCELED, e);
+            finish(dep, LoadStatus::CANCELED, e, lock);
         }
 
         // Clean dependency graph edges pointing to canceled jobs
@@ -531,87 +570,130 @@ void AsyncLoader::finish(std::unique_lock<std::mutex> & lock, const LoadJobPtr &
     });
 }
 
-void AsyncLoader::prioritize(const LoadJobPtr & job, ssize_t new_priority, std::unique_lock<std::mutex> & lock)
+void AsyncLoader::prioritize(const LoadJobPtr & job, size_t new_pool_id, std::unique_lock<std::mutex> & lock)
 {
     if (auto info = scheduled_jobs.find(job); info != scheduled_jobs.end())
     {
-        if (info->second.priority >= new_priority)
-            return; // Never lower priority
+        Pool & old_pool = pools[job->pool_id];
+        Pool & new_pool = pools[new_pool_id];
+        if (old_pool.priority >= new_pool.priority)
+            return; // Never lower priority or change pool leaving the same priority
 
         // Update priority and push job forward through ready queue if needed
-        if (info->second.ready_seqno)
-            ready_queue.erase(info->second.key());
-        info->second.priority = new_priority;
-        job->load_priority.store(new_priority); // Set user-facing priority (may affect executing jobs)
-        if (info->second.ready_seqno)
+        UInt64 ready_seqno = info->second.ready_seqno;
+
+        // Requeue job into the new pool queue without allocations
+        if (ready_seqno)
         {
-            NOEXCEPT_SCOPE({
-                ALLOW_ALLOCATIONS_IN_SCOPE;
-                ready_queue.emplace(info->second.key(), job);
-            });
+            new_pool.ready_queue.insert(old_pool.ready_queue.extract(ready_seqno));
+            if (canSpawnWorker(new_pool, lock))
+                spawn(new_pool, lock);
         }
 
+        // Set user-facing pool and priority (may affect executing jobs)
+        job->pool_id.store(new_pool_id);
+
         // Recurse into dependencies
         for (const auto & dep : job->dependencies)
-            prioritize(dep, new_priority, lock);
+            prioritize(dep, new_pool_id, lock);
     }
 }
 
 void AsyncLoader::enqueue(Info & info, const LoadJobPtr & job, std::unique_lock<std::mutex> & lock)
 {
-    chassert(!info.is_blocked());
+    chassert(!info.isBlocked());
     chassert(info.ready_seqno == 0);
     info.ready_seqno = ++last_ready_seqno;
+    Pool & pool = pools[job->pool_id];
     NOEXCEPT_SCOPE({
         ALLOW_ALLOCATIONS_IN_SCOPE;
-        ready_queue.emplace(info.key(), job);
+        pool.ready_queue.emplace(info.ready_seqno, job);
     });
 
     job->enqueued();
 
-    if (is_running && workers < max_threads)
-        spawn(lock);
+    if (canSpawnWorker(pool, lock))
+        spawn(pool, lock);
 }
 
-void AsyncLoader::spawn(std::unique_lock<std::mutex> &)
+bool AsyncLoader::canSpawnWorker(Pool & pool, std::unique_lock<std::mutex> &)
 {
-    workers++;
+    return is_running
+        && !pool.ready_queue.empty()
+        && pool.workers < pool.max_threads
+        && (!current_priority || *current_priority <= pool.priority);
+}
+
+bool AsyncLoader::canWorkerLive(Pool & pool, std::unique_lock<std::mutex> &)
+{
+    return is_running
+        && !pool.ready_queue.empty()
+        && pool.workers <= pool.max_threads
+        && (!current_priority || *current_priority <= pool.priority);
+}
+
+void AsyncLoader::updateCurrentPriorityAndSpawn(std::unique_lock<std::mutex> & lock)
+{
+    // Find current priority.
+    // NOTE: We assume low number of pools, so O(N) scans are fine.
+    std::optional<ssize_t> priority;
+    for (Pool & pool : pools)
+    {
+        if (pool.isActive() && (!priority || *priority < pool.priority))
+            priority = pool.priority;
+    }
+    current_priority = priority;
+
+    // Spawn workers in all pools with current priority
+    for (Pool & pool : pools)
+    {
+        for (size_t i = 0; canSpawnWorker(pool, lock) && i < pool.ready_queue.size(); i++)
+            spawn(pool, lock);
+    }
+}
+
+void AsyncLoader::spawn(Pool & pool, std::unique_lock<std::mutex> &)
+{
+    pool.workers++;
+    current_priority = pool.priority; // canSpawnWorker() ensures this would not decrease current_priority
     NOEXCEPT_SCOPE({
         ALLOW_ALLOCATIONS_IN_SCOPE;
-        pool.scheduleOrThrowOnError([this] { worker(); });
+        pool.thread_pool->scheduleOrThrowOnError([this, &pool] { worker(pool); });
     });
 }
 
-void AsyncLoader::worker()
+void AsyncLoader::worker(Pool & pool)
 {
     DENY_ALLOCATIONS_IN_SCOPE;
 
+    size_t pool_id = &pool - &*pools.begin();
     LoadJobPtr job;
     std::exception_ptr exception_from_job;
     while (true)
     {
         // This is inside the loop to also reset previous thread names set inside the jobs
-        setThreadName("AsyncLoader");
+        setThreadName(pool.name.c_str());
 
         {
             std::unique_lock lock{mutex};
 
             // Handle just executed job
             if (exception_from_job)
-                finish(lock, job, LoadStatus::FAILED, exception_from_job);
+                finish(job, LoadStatus::FAILED, exception_from_job, lock);
             else if (job)
-                finish(lock, job, LoadStatus::OK);
+                finish(job, LoadStatus::OK, {}, lock);
 
-            if (!is_running || ready_queue.empty() || workers > max_threads)
+            if (!canWorkerLive(pool, lock))
             {
-                workers--;
+                if (--pool.workers == 0)
+                    updateCurrentPriorityAndSpawn(lock); // It will spawn lower priority workers if needed
                 return;
             }
 
             // Take next job to be executed from the ready queue
-            auto it = ready_queue.begin();
+            auto it = pool.ready_queue.begin();
             job = it->second;
-            ready_queue.erase(it);
+            pool.ready_queue.erase(it);
             scheduled_jobs.find(job)->second.ready_seqno = 0; // This job is no longer in the ready queue
         }
 
@@ -619,7 +701,7 @@ void AsyncLoader::worker()
 
         try
         {
-            job->execute(job);
+            job->execute(pool_id, job);
             exception_from_job = {};
         }
         catch (...)

src/Common/AsyncLoader.h

@@ -12,7 +12,7 @@
 #include <base/types.h>
 #include <Common/CurrentMetrics.h>
 #include <Common/Stopwatch.h>
-#include <Common/ThreadPool.h>
+#include <Common/ThreadPool_fwd.h>
 
 
 namespace Poco { class Logger; }
@@ -46,22 +46,28 @@ class LoadJob : private boost::noncopyable
 {
 public:
     template <class Func, class LoadJobSetType>
-    LoadJob(LoadJobSetType && dependencies_, String name_, Func && func_, ssize_t priority_ = 0)
+    LoadJob(LoadJobSetType && dependencies_, String name_, size_t pool_id_, Func && func_)
         : dependencies(std::forward<LoadJobSetType>(dependencies_))
         , name(std::move(name_))
+        , pool_id(pool_id_)
         , func(std::forward<Func>(func_))
-        , load_priority(priority_)
     {}
 
     // Current job status.
     LoadStatus status() const;
     std::exception_ptr exception() const;
 
-    // Returns current value of a priority of the job. May differ from initial priority.
-    ssize_t priority() const;
+    // Returns pool in which the job is executing (was executed). May differ from initial pool and from current pool.
+    // Value is only valid (and constant) after execution started.
+    size_t executionPool() const;
+
+    // Returns current pool of the job. May differ from initial and execution pool.
+    // This value is intended for creating new jobs during this job execution.
+    // Value may change during job execution by `prioritize()`.
+    size_t pool() const;
 
     // Sync wait for a pending job to be finished: OK, FAILED or CANCELED status.
-    // Throws if job is FAILED or CANCELED. Returns or throws immediately on non-pending job.
+    // Throws if job is FAILED or CANCELED. Returns or throws immediately if called on non-pending job.
     void wait() const;
 
     // Wait for a job to reach any non PENDING status.
@@ -90,10 +96,11 @@ private:
 
     void scheduled();
     void enqueued();
-    void execute(const LoadJobPtr & self);
+    void execute(size_t pool, const LoadJobPtr & self);
 
+    std::atomic<size_t> execution_pool_id;
+    std::atomic<size_t> pool_id;
     std::function<void(const LoadJobPtr & self)> func;
-    std::atomic<ssize_t> load_priority;
 
     mutable std::mutex mutex;
     mutable std::condition_variable finished;
@@ -115,25 +122,25 @@ struct EmptyJobFunc
 template <class Func = EmptyJobFunc>
 LoadJobPtr makeLoadJob(LoadJobSet && dependencies, String name, Func && func = EmptyJobFunc())
 {
-    return std::make_shared<LoadJob>(std::move(dependencies), std::move(name), std::forward<Func>(func));
+    return std::make_shared<LoadJob>(std::move(dependencies), std::move(name), 0, std::forward<Func>(func));
 }
 
 template <class Func = EmptyJobFunc>
 LoadJobPtr makeLoadJob(const LoadJobSet & dependencies, String name, Func && func = EmptyJobFunc())
 {
-    return std::make_shared<LoadJob>(dependencies, std::move(name), std::forward<Func>(func));
+    return std::make_shared<LoadJob>(dependencies, std::move(name), 0, std::forward<Func>(func));
 }
 
 template <class Func = EmptyJobFunc>
-LoadJobPtr makeLoadJob(LoadJobSet && dependencies, ssize_t priority, String name, Func && func = EmptyJobFunc())
+LoadJobPtr makeLoadJob(LoadJobSet && dependencies, size_t pool_id, String name, Func && func = EmptyJobFunc())
 {
-    return std::make_shared<LoadJob>(std::move(dependencies), std::move(name), std::forward<Func>(func), priority);
+    return std::make_shared<LoadJob>(std::move(dependencies), std::move(name), pool_id, std::forward<Func>(func));
 }
 
 template <class Func = EmptyJobFunc>
-LoadJobPtr makeLoadJob(const LoadJobSet & dependencies, ssize_t priority, String name, Func && func = EmptyJobFunc())
+LoadJobPtr makeLoadJob(const LoadJobSet & dependencies, size_t pool_id, String name, Func && func = EmptyJobFunc())
 {
-    return std::make_shared<LoadJob>(dependencies, std::move(name), std::forward<Func>(func), priority);
+    return std::make_shared<LoadJob>(dependencies, std::move(name), pool_id, std::forward<Func>(func));
 }
 
 // Represents a logically connected set of LoadJobs required to achieve some goals (final LoadJob in the set).
@@ -185,7 +192,7 @@ inline void scheduleLoad(const LoadTaskPtrs & tasks)
 }
 
 template <class... Args>
-inline void scheduleLoad(Args && ... args)
+inline void scheduleLoadAll(Args && ... args)
 {
     (scheduleLoad(std::forward<Args>(args)), ...);
 }
@@ -208,16 +215,16 @@ inline void waitLoad(const LoadTaskPtrs & tasks)
 }
 
 template <class... Args>
-inline void waitLoad(Args && ... args)
+inline void waitLoadAll(Args && ... args)
 {
     (waitLoad(std::forward<Args>(args)), ...);
 }
 
 template <class... Args>
-inline void scheduleAndWaitLoad(Args && ... args)
+inline void scheduleAndWaitLoadAll(Args && ... args)
 {
-    scheduleLoad(std::forward<Args>(args)...);
-    waitLoad(std::forward<Args>(args)...);
+    scheduleLoadAll(std::forward<Args>(args)...);
+    waitLoadAll(std::forward<Args>(args)...);
 }
 
 inline LoadJobSet getGoals(const LoadTaskPtrs & tasks)
@@ -228,6 +235,14 @@ inline LoadJobSet getGoals(const LoadTaskPtrs & tasks)
     return result;
 }
 
+inline LoadJobSet getGoalsOr(const LoadTaskPtrs & tasks, const LoadJobSet & alternative)
+{
+    LoadJobSet result;
+    for (const auto & task : tasks)
+        result.insert(task->goals().begin(), task->goals().end());
+    return result.empty() ? alternative : result;
+}
+
 inline LoadJobSet joinJobs(const LoadJobSet & jobs1, const LoadJobSet & jobs2)
 {
     LoadJobSet result;
@@ -251,100 +266,117 @@ inline LoadTaskPtrs joinTasks(const LoadTaskPtrs & tasks1, const LoadTaskPtrs &
     return result;
 }
 
-// `AsyncLoader` is a scheduler for DAG of `LoadJob`s. It tracks dependencies and priorities of jobs.
+// `AsyncLoader` is a scheduler for DAG of `LoadJob`s. It tracks job dependencies and priorities.
 // Basic usage example:
+//     // Start async_loader with two thread pools (0=bg, 1=fg):
+//     AsyncLoader async_loader({
+//         {"BgPool", CurrentMetrics::AsyncLoaderThreads, CurrentMetrics::AsyncLoaderThreadsActive, .max_threads = 1, .priority = 0}
+//         {"FgPool", CurrentMetrics::AsyncLoaderThreads, CurrentMetrics::AsyncLoaderThreadsActive, .max_threads = 2, .priority = 1}
+//     });
+//
+//     // Create and schedule a task consisting of three jobs. Job1 has no dependencies and is run first.
+//     // Job2 and job3 depend on job1 and are run only after job1 completion.
 //     auto job_func = [&] (const LoadJobPtr & self) {
-//         LOG_TRACE(log, "Executing load job '{}' with priority '{}'", self->name, self->priority());
+//         LOG_TRACE(log, "Executing load job '{}' in pool '{}'", self->name, async_loader->getPoolName(self->pool()));
 //     };
-//     auto job1 = makeLoadJob({}, "job1", job_func);
-//     auto job2 = makeLoadJob({ job1 }, "job2", job_func);
-//     auto job3 = makeLoadJob({ job1 }, "job3", job_func);
+//     auto job1 = makeLoadJob({}, "job1", /* pool_id = */ 0, job_func);
+//     auto job2 = makeLoadJob({ job1 }, "job2", /* pool_id = */ 0, job_func);
+//     auto job3 = makeLoadJob({ job1 }, "job3", /* pool_id = */ 0, job_func);
 //     auto task = makeLoadTask(async_loader, { job1, job2, job3 });
 //     task.schedule();
-// Here we have created and scheduled a task consisting of three jobs. Job1 has no dependencies and is run first.
-// Job2 and job3 depend on job1 and are run only after job1 completion. Another thread may prioritize a job and wait for it:
-//     async_loader->prioritize(job3, /* priority = */ 1); // higher priority jobs are run first, default priority is zero.
+//
+//     // Another thread may prioritize a job by changing its pool and wait for it:
+//     async_loader->prioritize(job3, /* pool_id = */ 1); // higher priority jobs are run first, default priority is zero.
 //     job3->wait(); // blocks until job completion or cancellation and rethrow an exception (if any)
 //
-// AsyncLoader tracks state of all scheduled jobs. Job lifecycle is the following:
-// 1)  Job is constructed with PENDING status and initial priority. The job is placed into a task.
-// 2)  The task is scheduled with all its jobs and their dependencies. A scheduled job may be ready (i.e. have all its dependencies finished) or blocked.
-// 3a) When all dependencies are successfully executed, the job became ready. A ready job is enqueued into the ready queue.
+// Every job has a pool associated with it. AsyncLoader starts every job in its thread pool.
+// Each pool has a constant priority and a mutable maximum number of threads.
+// Higher priority (greater `pool.priority` value) jobs are run first.
+// No job with lower priority is started while there is at least one higher priority job ready or running.
+//
+// Job priority can be elevated (but cannot be lowered)
+// (a) if either it has a dependent job with higher priority:
+//     in this case the priority and the pool of a dependent job is inherited during `schedule()` call;
+// (b) or job was explicitly prioritized by `prioritize(job, higher_priority_pool)` call:
+//     this also leads to a priority inheritance for all the dependencies.
+// Value stored in load job `pool_id` field is atomic and can be changed even during job execution.
+// Job is, of course, not moved from its initial thread pool, but it should use `self->pool()` for
+// all new jobs it create to avoid priority inversion.
+//
+// === IMPLEMENTATION DETAILS ===
+// All possible states and statuses of a job:
+//                       .---------- scheduled ----------.
+//  ctor --> assigned --> blocked --> ready --> executing --> finished ------> removed --> dtor
+//  STATUS: '------------------ PENDING -----------------'   '-- OK|FAILED|CANCELED --'
+//
+// AsyncLoader tracks state of all scheduled and finished jobs. Job lifecycle is the following:
+// 1)  A job is constructed with PENDING status and assigned to a pool. The job is placed into a task.
+// 2)  The task is scheduled with all its jobs and their dependencies. A scheduled job may be ready, blocked (and later executing).
+// 3a) When all dependencies are successfully finished, the job became ready. A ready job is enqueued into the ready queue of its pool.
 // 3b) If at least one of the job dependencies is failed or canceled, then this job is canceled (with all it's dependent jobs as well).
 //     On cancellation an ASYNC_LOAD_CANCELED exception is generated and saved inside LoadJob object. The job status is changed to CANCELED.
 //     Exception is rethrown by any existing or new `wait()` call. The job is moved to the set of the finished jobs.
-// 4)  The scheduled pending ready job starts execution by a worker. The job is dequeued. Callback `job_func` is called.
-//     Status of an executing job is PENDING. And it is still considered as a scheduled job by AsyncLoader.
-//     Note that `job_func` of a CANCELED job is never executed.
+// 4)  The ready job starts execution by a worker. The job is dequeued. Callback `job_func` is called.
+//     Status of an executing job is PENDING. Note that `job_func` of a CANCELED job is never executed.
 // 5a) On successful execution the job status is changed to OK and all existing and new `wait()` calls finish w/o exceptions.
 // 5b) Any exception thrown out of `job_func` is wrapped into an ASYNC_LOAD_FAILED exception and saved inside LoadJob.
 //     The job status is changed to FAILED. All the dependent jobs are canceled. The exception is rethrown from all existing and new `wait()` calls.
 // 6)  The job is no longer considered as scheduled and is instead moved to the finished jobs set. This is just for introspection of the finished jobs.
 // 7)  The task containing this job is destructed or `remove()` is explicitly called. The job is removed from the finished job set.
 // 8)  The job is destructed.
-//
-// Every job has a priority associated with it. AsyncLoader runs higher priority (greater `priority` value) jobs first. Job priority can be elevated
-// (a) if either it has a dependent job with higher priority (in this case priority of a dependent job is inherited);
-// (b) or job was explicitly prioritized by `prioritize(job, higher_priority)` call (this also leads to a priority inheritance for all the dependencies).
-// Note that to avoid priority inversion `job_func` should use `self->priority()` to schedule new jobs in AsyncLoader or any other pool.
-// Value stored in load job priority field is atomic and can be increased even during job execution.
-//
-// When a task is scheduled it can contain dependencies on previously scheduled jobs. These jobs can have any status. If job A being scheduled depends on
-// another job B that is not yet scheduled, then job B will also be scheduled (even if the task does not contain it).
 class AsyncLoader : private boost::noncopyable
 {
 private:
-    // Key of a pending job in the ready queue.
-    struct ReadyKey
+    // Thread pool for job execution.
+    // Pools control the following aspects of job execution:
+    // 1) Concurrency: Amount of concurrently executing jobs in a pool is `max_threads`.
+    // 2) Priority: As long as there is executing worker with higher priority, workers with lower priorities are not started
+    //    (although, they can finish last job started before higher priority jobs appeared)
+    struct Pool
     {
-        ssize_t priority; // Ascending order
-        ssize_t initial_priority; // Ascending order
-        UInt64 ready_seqno; // Descending order
+        const String name;
+        const ssize_t priority;
+        std::unique_ptr<ThreadPool> thread_pool; // NOTE: we avoid using a `ThreadPool` queue to be able to move jobs between pools.
+        std::map<UInt64, LoadJobPtr> ready_queue; // FIFO queue of jobs to be executed in this pool. Map is used for faster erasing. Key is `ready_seqno`
+        size_t max_threads; // Max number of workers to be spawn
+        size_t workers = 0; // Number of currently execution workers
 
-        bool operator<(const ReadyKey & rhs) const
-        {
-            if (priority > rhs.priority)
-                return true;
-            if (priority < rhs.priority)
-                return false;
-            if (initial_priority > rhs.initial_priority)
-                return true;
-            if (initial_priority < rhs.initial_priority)
-                return false;
-            return ready_seqno < rhs.ready_seqno;
-        }
+        bool isActive() const { return workers > 0 || !ready_queue.empty(); }
     };
 
     // Scheduling information for a pending job.
     struct Info
     {
-        ssize_t initial_priority = 0; // Initial priority passed into schedule().
-        ssize_t priority = 0; // Elevated priority, due to priority inheritance or prioritize().
         size_t dependencies_left = 0; // Current number of dependencies on pending jobs.
         UInt64 ready_seqno = 0; // Zero means that job is not in ready queue.
         LoadJobSet dependent_jobs; // Set of jobs dependent on this job.
 
-        // Three independent states of a non-finished job.
-        bool is_blocked() const { return dependencies_left > 0; }
-        bool is_ready() const { return dependencies_left == 0 && ready_seqno > 0; }
-        bool is_executing() const { return dependencies_left == 0 && ready_seqno == 0; }
-
-        // Get key of a ready job
-        ReadyKey key() const
-        {
-            return {.priority = priority, .initial_priority = initial_priority, .ready_seqno = ready_seqno};
-        }
+        // Three independent states of a scheduled job.
+        bool isBlocked() const { return dependencies_left > 0; }
+        bool isReady() const { return dependencies_left == 0 && ready_seqno > 0; }
+        bool isExecuting() const { return dependencies_left == 0 && ready_seqno == 0; }
     };
 
 public:
     using Metric = CurrentMetrics::Metric;
 
-    AsyncLoader(Metric metric_threads, Metric metric_active_threads, size_t max_threads_, bool log_failures_, bool log_progress_);
+    // Helper struct for AsyncLoader construction
+    struct PoolInitializer
+    {
+        String name;
+        Metric metric_threads;
+        Metric metric_active_threads;
+        size_t max_threads;
+        ssize_t priority;
+    };
 
+    AsyncLoader(std::vector<PoolInitializer> pool_initializers, bool log_failures_, bool log_progress_);
+
+    // Stops AsyncLoader before destruction
     // WARNING: all tasks instances should be destructed before associated AsyncLoader.
     ~AsyncLoader();
 
-    // Start workers to execute scheduled load jobs.
+    // Start workers to execute scheduled load jobs. Note that AsyncLoader is constructed as already started.
     void start();
 
     // Wait for all load jobs to finish, including all new jobs. So at first take care to stop adding new jobs.
@@ -356,28 +388,32 @@ public:
     //  - or canceled using ~Task() or remove() later.
     void stop();
 
-    // Schedule all jobs of given `task` and their dependencies (if any, not scheduled yet).
-    // Higher priority jobs (with greater `job->priority()` value) are executed earlier.
-    // All dependencies of a scheduled job inherit its priority if it is higher. This way higher priority job
-    // never wait for (blocked by) lower priority jobs. No priority inversion is possible.
+    // Schedule all jobs of given `task` and their dependencies (even if they are not in task).
+    // All dependencies of a scheduled job inherit its pool if it has higher priority. This way higher priority job
+    // never waits for (blocked by) lower priority jobs. No priority inversion is possible.
+    // Idempotent: multiple schedule() calls for the same job are no-op.
     // Note that `task` destructor ensures that all its jobs are finished (OK, FAILED or CANCELED)
     // and are removed from AsyncLoader, so it is thread-safe to destroy them.
     void schedule(LoadTask & task);
     void schedule(const LoadTaskPtr & task);
 
     // Schedule all tasks atomically. To ensure only highest priority jobs among all tasks are run first.
-    void schedule(const std::vector<LoadTaskPtr> & tasks);
+    void schedule(const LoadTaskPtrs & tasks);
 
     // Increase priority of a job and all its dependencies recursively.
-    void prioritize(const LoadJobPtr & job, ssize_t new_priority);
+    // Jobs from higher (than `new_pool`) priority pools are not changed.
+    void prioritize(const LoadJobPtr & job, size_t new_pool);
 
     // Remove finished jobs, cancel scheduled jobs, wait for executing jobs to finish and remove them.
     void remove(const LoadJobSet & jobs);
 
-    // Increase or decrease maximum number of simultaneously executing jobs.
-    void setMaxThreads(size_t value);
+    // Increase or decrease maximum number of simultaneously executing jobs in `pool`.
+    void setMaxThreads(size_t pool, size_t value);
+
+    size_t getMaxThreads(size_t pool) const;
+    const String & getPoolName(size_t pool) const;
+    ssize_t getPoolPriority(size_t pool) const;
 
-    size_t getMaxThreads() const;
     size_t getScheduledJobCount() const;
 
     // Helper class for introspection
@@ -385,11 +421,10 @@ public:
     {
         LoadJobPtr job;
         size_t dependencies_left = 0;
-        bool is_executing = false;
+        UInt64 ready_seqno = 0;
         bool is_blocked = false;
         bool is_ready = false;
-        std::optional<ssize_t> initial_priority;
-        std::optional<UInt64> ready_seqno;
+        bool is_executing = false;
     };
 
     // For introspection and debug only, see `system.async_loader` table
@@ -398,42 +433,32 @@ public:
 private:
     void checkCycle(const LoadJobSet & jobs, std::unique_lock<std::mutex> & lock);
     String checkCycleImpl(const LoadJobPtr & job, LoadJobSet & left, LoadJobSet & visited, std::unique_lock<std::mutex> & lock);
-    void finish(std::unique_lock<std::mutex> & lock, const LoadJobPtr & job, LoadStatus status, std::exception_ptr exception_from_job = {});
+    void finish(const LoadJobPtr & job, LoadStatus status, std::exception_ptr exception_from_job, std::unique_lock<std::mutex> & lock);
     void scheduleImpl(const LoadJobSet & input_jobs);
     void gatherNotScheduled(const LoadJobPtr & job, LoadJobSet & jobs, std::unique_lock<std::mutex> & lock);
-    void prioritize(const LoadJobPtr & job, ssize_t new_priority, std::unique_lock<std::mutex> & lock);
+    void prioritize(const LoadJobPtr & job, size_t new_pool_id, std::unique_lock<std::mutex> & lock);
     void enqueue(Info & info, const LoadJobPtr & job, std::unique_lock<std::mutex> & lock);
-    void spawn(std::unique_lock<std::mutex> &);
-    void worker();
+    bool canSpawnWorker(Pool & pool, std::unique_lock<std::mutex> &);
+    bool canWorkerLive(Pool & pool, std::unique_lock<std::mutex> &);
+    void updateCurrentPriorityAndSpawn(std::unique_lock<std::mutex> &);
+    void spawn(Pool & pool, std::unique_lock<std::mutex> &);
+    void worker(Pool & pool);
 
     // Logging
     const bool log_failures; // Worker should log all exceptions caught from job functions.
     const bool log_progress; // Periodically log total progress
     Poco::Logger * log;
-    std::chrono::system_clock::time_point busy_period_start_time;
-    AtomicStopwatch stopwatch;
-    size_t old_jobs = 0; // Number of jobs that were finished in previous busy period (for correct progress indication)
 
     mutable std::mutex mutex; // Guards all the fields below.
-    bool is_running = false;
-
-    // Full set of scheduled pending jobs along with scheduling info.
-    std::unordered_map<LoadJobPtr, Info> scheduled_jobs;
-
-    // Subset of scheduled pending non-blocked jobs (waiting for a worker to be executed).
-    // Represent a queue of jobs in order of decreasing priority and FIFO for jobs with equal priorities.
-    std::map<ReadyKey, LoadJobPtr> ready_queue;
-
-    // Set of finished jobs (for introspection only, until jobs are removed).
-    LoadJobSet finished_jobs;
-
-    // Increasing counter for `ReadyKey` assignment (to preserve FIFO order of the jobs with equal priorities).
-    UInt64 last_ready_seqno = 0;
-
-    // For executing jobs. Note that we avoid using an internal queue of the pool to be able to prioritize jobs.
-    size_t max_threads;
-    size_t workers = 0;
-    ThreadPool pool;
+    bool is_running = true;
+    std::optional<ssize_t> current_priority; // highest priority among active pools
+    UInt64 last_ready_seqno = 0; // Increasing counter for ready queue keys.
+    std::unordered_map<LoadJobPtr, Info> scheduled_jobs; // Full set of scheduled pending jobs along with scheduling info.
+    std::vector<Pool> pools; // Thread pools for job execution and ready queues
+    LoadJobSet finished_jobs; // Set of finished jobs (for introspection only, until jobs are removed).
+    AtomicStopwatch stopwatch; // For progress indication
+    size_t old_jobs = 0; // Number of jobs that were finished in previous busy period (for correct progress indication)
+    std::chrono::system_clock::time_point busy_period_start_time;
 };
 
 }

src/Common/AsynchronousMetrics.cpp

@@ -1041,18 +1041,16 @@ void AsynchronousMetrics::update(TimePoint update_time)
                 // It doesn't read the EOL itself.
                 ++cpuinfo->position();
 
-                if (s.rfind("processor", 0) == 0)
+                static constexpr std::string_view PROCESSOR = "processor";
+                if (s.starts_with(PROCESSOR))
                 {
                     /// s390x example: processor 0: version = FF, identification = 039C88, machine = 3906
                     /// non s390x example: processor : 0
-                    if (auto colon = s.find_first_of(':'))
-                    {
-#ifdef __s390x__
-                        core_id = std::stoi(s.substr(10)); /// 10: length of "processor" plus 1
-#else
-                        core_id = std::stoi(s.substr(colon + 2));
-#endif
-                    }
+                    auto core_id_start = std::ssize(PROCESSOR);
+                    while (core_id_start < std::ssize(s) && !std::isdigit(s[core_id_start]))
+                        ++core_id_start;
+
+                    core_id = std::stoi(s.substr(core_id_start));
                 }
                 else if (s.rfind("cpu MHz", 0) == 0)
                 {

src/Common/Priority.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <base/types.h>
+
+/// Common type for priority values.
+/// Separate type (rather than `Int64` is used just to avoid implicit conversion errors and to default-initialize
+struct Priority
+{
+    Int64 value = 0; /// Note that lower value means higher priority.
+    constexpr operator Int64() const { return value; } /// NOLINT
+};

src/Common/ThreadPool.cpp

@@ -123,7 +123,7 @@ void ThreadPoolImpl<Thread>::setQueueSize(size_t value)
 
 template <typename Thread>
 template <typename ReturnType>
-ReturnType ThreadPoolImpl<Thread>::scheduleImpl(Job job, ssize_t priority, std::optional<uint64_t> wait_microseconds, bool propagate_opentelemetry_tracing_context)
+ReturnType ThreadPoolImpl<Thread>::scheduleImpl(Job job, Priority priority, std::optional<uint64_t> wait_microseconds, bool propagate_opentelemetry_tracing_context)
 {
     auto on_error = [&](const std::string & reason)
     {
@@ -231,19 +231,19 @@ void ThreadPoolImpl<Thread>::startNewThreadsNoLock()
 }
 
 template <typename Thread>
-void ThreadPoolImpl<Thread>::scheduleOrThrowOnError(Job job, ssize_t priority)
+void ThreadPoolImpl<Thread>::scheduleOrThrowOnError(Job job, Priority priority)
 {
     scheduleImpl<void>(std::move(job), priority, std::nullopt);
 }
 
 template <typename Thread>
-bool ThreadPoolImpl<Thread>::trySchedule(Job job, ssize_t priority, uint64_t wait_microseconds) noexcept
+bool ThreadPoolImpl<Thread>::trySchedule(Job job, Priority priority, uint64_t wait_microseconds) noexcept
 {
     return scheduleImpl<bool>(std::move(job), priority, wait_microseconds);
 }
 
 template <typename Thread>
-void ThreadPoolImpl<Thread>::scheduleOrThrow(Job job, ssize_t priority, uint64_t wait_microseconds, bool propagate_opentelemetry_tracing_context)
+void ThreadPoolImpl<Thread>::scheduleOrThrow(Job job, Priority priority, uint64_t wait_microseconds, bool propagate_opentelemetry_tracing_context)
 {
     scheduleImpl<void>(std::move(job), priority, wait_microseconds, propagate_opentelemetry_tracing_context);
 }

src/Common/ThreadPool.h

@@ -18,6 +18,7 @@
 #include <Common/OpenTelemetryTraceContext.h>
 #include <Common/CurrentMetrics.h>
 #include <Common/ThreadPool_fwd.h>
+#include <Common/Priority.h>
 #include <base/scope_guard.h>
 
 /** Very simple thread pool similar to boost::threadpool.
@@ -59,17 +60,17 @@ public:
     /// If any thread was throw an exception, first exception will be rethrown from this method,
     ///  and exception will be cleared.
     /// Also throws an exception if cannot create thread.
-    /// Priority: greater is higher.
+    /// Priority: lower is higher.
     /// NOTE: Probably you should call wait() if exception was thrown. If some previously scheduled jobs are using some objects,
     /// located on stack of current thread, the stack must not be unwinded until all jobs finished. However,
     /// if ThreadPool is a local object, it will wait for all scheduled jobs in own destructor.
-    void scheduleOrThrowOnError(Job job, ssize_t priority = 0);
+    void scheduleOrThrowOnError(Job job, Priority priority = {});
 
     /// Similar to scheduleOrThrowOnError(...). Wait for specified amount of time and schedule a job or return false.
-    bool trySchedule(Job job, ssize_t priority = 0, uint64_t wait_microseconds = 0) noexcept;
+    bool trySchedule(Job job, Priority priority = {}, uint64_t wait_microseconds = 0) noexcept;
 
     /// Similar to scheduleOrThrowOnError(...). Wait for specified amount of time and schedule a job or throw an exception.
-    void scheduleOrThrow(Job job, ssize_t priority = 0, uint64_t wait_microseconds = 0, bool propagate_opentelemetry_tracing_context = true);
+    void scheduleOrThrow(Job job, Priority priority = {}, uint64_t wait_microseconds = 0, bool propagate_opentelemetry_tracing_context = true);
 
     /// Wait for all currently active jobs to be done.
     /// You may call schedule and wait many times in arbitrary order.
@@ -123,15 +124,15 @@ private:
     struct JobWithPriority
     {
         Job job;
-        ssize_t priority;
+        Priority priority;
         DB::OpenTelemetry::TracingContextOnThread thread_trace_context;
 
-        JobWithPriority(Job job_, ssize_t priority_, const DB::OpenTelemetry::TracingContextOnThread& thread_trace_context_)
+        JobWithPriority(Job job_, Priority priority_, const DB::OpenTelemetry::TracingContextOnThread & thread_trace_context_)
             : job(job_), priority(priority_), thread_trace_context(thread_trace_context_) {}
 
         bool operator<(const JobWithPriority & rhs) const
         {
-            return priority < rhs.priority;
+            return priority > rhs.priority; // Reversed for `priority_queue` max-heap to yield minimum value (i.e. highest priority) first
         }
     };
 
@@ -141,7 +142,7 @@ private:
     std::stack<OnDestroyCallback> on_destroy_callbacks;
 
     template <typename ReturnType>
-    ReturnType scheduleImpl(Job job, ssize_t priority, std::optional<uint64_t> wait_microseconds, bool propagate_opentelemetry_tracing_context = true);
+    ReturnType scheduleImpl(Job job, Priority priority, std::optional<uint64_t> wait_microseconds, bool propagate_opentelemetry_tracing_context = true);
 
     void worker(typename std::list<Thread>::iterator thread_it);
 
@@ -227,7 +228,7 @@ public:
             DB::ThreadStatus thread_status;
             std::apply(function, arguments);
         },
-        0, // default priority
+        {}, // default priority
         0, // default wait_microseconds
         propagate_opentelemetry_context
         );

src/Common/tests/gtest_async_loader.cpp

@@ -30,6 +30,11 @@ namespace DB::ErrorCodes
     extern const int ASYNC_LOAD_CANCELED;
 }
 
+struct Initializer {
+    size_t max_threads = 1;
+    ssize_t priority = 0;
+};
+
 struct AsyncLoaderTest
 {
     AsyncLoader loader;
@@ -37,10 +42,34 @@ struct AsyncLoaderTest
     std::mutex rng_mutex;
     pcg64 rng{randomSeed()};
 
+    explicit AsyncLoaderTest(std::vector<Initializer> initializers)
+        : loader(getPoolInitializers(initializers), /* log_failures = */ false, /* log_progress = */ false)
+    {
+        loader.stop(); // All tests call `start()` manually to better control ordering
+    }
+
     explicit AsyncLoaderTest(size_t max_threads = 1)
-        : loader(CurrentMetrics::TablesLoaderThreads, CurrentMetrics::TablesLoaderThreadsActive, max_threads, /* log_failures = */ false, /* log_progress = */ false)
+        : AsyncLoaderTest({{.max_threads = max_threads}})
     {}
 
+    std::vector<AsyncLoader::PoolInitializer> getPoolInitializers(std::vector<Initializer> initializers)
+    {
+        std::vector<AsyncLoader::PoolInitializer> result;
+        size_t pool_id = 0;
+        for (auto & desc : initializers)
+        {
+            result.push_back({
+                .name = fmt::format("Pool{}", pool_id),
+                .metric_threads = CurrentMetrics::TablesLoaderThreads,
+                .metric_active_threads = CurrentMetrics::TablesLoaderThreadsActive,
+                .max_threads = desc.max_threads,
+                .priority = desc.priority
+            });
+            pool_id++;
+        }
+        return result;
+    }
+
     template <typename T>
     T randomInt(T from, T to)
     {
@@ -114,16 +143,19 @@ struct AsyncLoaderTest
 
 TEST(AsyncLoader, Smoke)
 {
-    AsyncLoaderTest t(2);
+    AsyncLoaderTest t({
+        {.max_threads = 2, .priority = 0},
+        {.max_threads = 2, .priority = -1},
+    });
 
-    static constexpr ssize_t low_priority = -1;
+    static constexpr ssize_t low_priority_pool = 1;
 
     std::atomic<size_t> jobs_done{0};
     std::atomic<size_t> low_priority_jobs_done{0};
 
     auto job_func = [&] (const LoadJobPtr & self) {
         jobs_done++;
-        if (self->priority() == low_priority)
+        if (self->pool() == low_priority_pool)
             low_priority_jobs_done++;
     };
 
@@ -135,7 +167,7 @@ TEST(AsyncLoader, Smoke)
         auto job3 = makeLoadJob({ job2 }, "job3", job_func);
         auto job4 = makeLoadJob({ job2 }, "job4", job_func);
         auto task2 = t.schedule({ job3, job4 });
-        auto job5 = makeLoadJob({ job3, job4 }, low_priority, "job5", job_func);
+        auto job5 = makeLoadJob({ job3, job4 }, low_priority_pool, "job5", job_func);
         task2->merge(t.schedule({ job5 }));
 
         std::thread waiter_thread([=] { job5->wait(); });
@@ -536,7 +568,7 @@ TEST(AsyncLoader, TestOverload)
     AsyncLoaderTest t(3);
     t.loader.start();
 
-    size_t max_threads = t.loader.getMaxThreads();
+    size_t max_threads = t.loader.getMaxThreads(/* pool = */ 0);
     std::atomic<int> executing{0};
 
     for (int concurrency = 4; concurrency <= 8; concurrency++)
@@ -562,13 +594,24 @@ TEST(AsyncLoader, TestOverload)
 
 TEST(AsyncLoader, StaticPriorities)
 {
-    AsyncLoaderTest t(1);
+    AsyncLoaderTest t({
+        {.max_threads = 1, .priority = 0},
+        {.max_threads = 1, .priority = 1},
+        {.max_threads = 1, .priority = 2},
+        {.max_threads = 1, .priority = 3},
+        {.max_threads = 1, .priority = 4},
+        {.max_threads = 1, .priority = 5},
+        {.max_threads = 1, .priority = 6},
+        {.max_threads = 1, .priority = 7},
+        {.max_threads = 1, .priority = 8},
+        {.max_threads = 1, .priority = 9},
+    });
 
     std::string schedule;
 
     auto job_func = [&] (const LoadJobPtr & self)
     {
-        schedule += fmt::format("{}{}", self->name, self->priority());
+        schedule += fmt::format("{}{}", self->name, self->pool());
     };
 
     std::vector<LoadJobPtr> jobs;
@@ -588,21 +631,110 @@ TEST(AsyncLoader, StaticPriorities)
     ASSERT_EQ(schedule, "A9E9D9F9G9H9C4B3");
 }
 
+TEST(AsyncLoader, SimplePrioritization)
+{
+    AsyncLoaderTest t({
+        {.max_threads = 1, .priority = 0},
+        {.max_threads = 1, .priority = 1},
+        {.max_threads = 1, .priority = 2},
+    });
+
+    t.loader.start();
+
+    std::atomic<int> executed{0}; // Number of previously executed jobs (to test execution order)
+    LoadJobPtr job_to_prioritize;
+
+    auto job_func_A_booster = [&] (const LoadJobPtr &)
+    {
+        ASSERT_EQ(executed++, 0);
+        t.loader.prioritize(job_to_prioritize, 2);
+    };
+
+    auto job_func_B_tester = [&] (const LoadJobPtr &)
+    {
+        ASSERT_EQ(executed++, 2);
+    };
+
+    auto job_func_C_boosted = [&] (const LoadJobPtr &)
+    {
+        ASSERT_EQ(executed++, 1);
+    };
+
+    std::vector<LoadJobPtr> jobs;
+    jobs.push_back(makeLoadJob({}, 1, "A", job_func_A_booster)); // 0
+    jobs.push_back(makeLoadJob({jobs[0]}, 1, "B", job_func_B_tester)); // 1
+    jobs.push_back(makeLoadJob({}, 0, "C", job_func_C_boosted)); // 2
+    auto task = makeLoadTask(t.loader, { jobs.begin(), jobs.end() });
+
+    job_to_prioritize = jobs[2]; // C
+
+    scheduleAndWaitLoadAll(task);
+}
+
 TEST(AsyncLoader, DynamicPriorities)
 {
-    AsyncLoaderTest t(1);
+    AsyncLoaderTest t({
+        {.max_threads = 1, .priority = 0},
+        {.max_threads = 1, .priority = 1},
+        {.max_threads = 1, .priority = 2},
+        {.max_threads = 1, .priority = 3},
+        {.max_threads = 1, .priority = 4},
+        {.max_threads = 1, .priority = 5},
+        {.max_threads = 1, .priority = 6},
+        {.max_threads = 1, .priority = 7},
+        {.max_threads = 1, .priority = 8},
+        {.max_threads = 1, .priority = 9},
+    });
 
     for (bool prioritize : {false, true})
     {
+        // Although all pools have max_threads=1, workers from different pools can run simultaneously just after `prioritize()` call
+        std::barrier sync(2);
+        bool wait_sync = prioritize;
+        std::mutex schedule_mutex;
         std::string schedule;
 
         LoadJobPtr job_to_prioritize;
 
+        // Order of execution of jobs D and E after prioritization is undefined, because it depend on `ready_seqno`
+        // (Which depends on initial `schedule()` order, which in turn depend on `std::unordered_map` order)
+        // So we have to obtain `ready_seqno` to be sure.
+        UInt64 ready_seqno_D = 0;
+        UInt64 ready_seqno_E = 0;
+
         auto job_func = [&] (const LoadJobPtr & self)
         {
+            {
+                std::unique_lock lock{schedule_mutex};
+                schedule += fmt::format("{}{}", self->name, self->executionPool());
+            }
+
             if (prioritize && self->name == "C")
-                t.loader.prioritize(job_to_prioritize, 9); // dynamic prioritization
-            schedule += fmt::format("{}{}", self->name, self->priority());
+            {
+                for (const auto & state : t.loader.getJobStates())
+                {
+                    if (state.job->name == "D")
+                        ready_seqno_D = state.ready_seqno;
+                    if (state.job->name == "E")
+                        ready_seqno_E = state.ready_seqno;
+                }
+
+                // Jobs D and E should be enqueued at the moment
+                ASSERT_LT(0, ready_seqno_D);
+                ASSERT_LT(0, ready_seqno_E);
+
+                // Dynamic prioritization G0 -> G9
+                // Note that it will spawn concurrent worker in higher priority pool
+                t.loader.prioritize(job_to_prioritize, 9);
+
+                sync.arrive_and_wait(); // (A) wait for higher priority worker (B) to test they can be concurrent
+            }
+
+            if (wait_sync && (self->name == "D" || self->name == "E"))
+            {
+                wait_sync = false;
+                sync.arrive_and_wait(); // (B)
+            }
         };
 
         // Job DAG with initial priorities. During execution of C4, job G0 priority is increased to G9, postponing B3 job executing.
@@ -624,14 +756,19 @@ TEST(AsyncLoader, DynamicPriorities)
         jobs.push_back(makeLoadJob({ jobs[6] }, 0, "H", job_func)); // 7
         auto task = t.schedule({ jobs.begin(), jobs.end() });
 
-        job_to_prioritize = jobs[6];
+        job_to_prioritize = jobs[6]; // G
 
         t.loader.start();
         t.loader.wait();
         t.loader.stop();
 
         if (prioritize)
+        {
+            if (ready_seqno_D < ready_seqno_E)
+                ASSERT_EQ(schedule, "A4C4D9E9F9G9B3H0");
+            else
                 ASSERT_EQ(schedule, "A4C4E9D9F9G9B3H0");
+        }
         else
             ASSERT_EQ(schedule, "A4C4B3E2D1F0G0H0");
     }
@@ -742,8 +879,64 @@ TEST(AsyncLoader, SetMaxThreads)
         syncs[idx]->arrive_and_wait(); // (A)
         sync_index++;
         if (sync_index < syncs.size())
-            t.loader.setMaxThreads(max_threads_values[sync_index]);
+            t.loader.setMaxThreads(/* pool = */ 0, max_threads_values[sync_index]);
         syncs[idx]->arrive_and_wait(); // (B) this sync point is required to allow `executing` value to go back down to zero after we change number of workers
     }
     t.loader.wait();
 }
+
+TEST(AsyncLoader, DynamicPools)
+{
+    const size_t max_threads[] { 2, 10 };
+    const int jobs_in_chain = 16;
+    AsyncLoaderTest t({
+        {.max_threads = max_threads[0], .priority = 0},
+        {.max_threads = max_threads[1], .priority = 1},
+    });
+
+    t.loader.start();
+
+    std::atomic<size_t> executing[2] { 0, 0 }; // Number of currently executing jobs per pool
+
+    for (int concurrency = 1; concurrency <= 12; concurrency++)
+    {
+        std::atomic<bool> boosted{false}; // Visible concurrency was increased
+        std::atomic<int> left{concurrency * jobs_in_chain / 2}; // Number of jobs to start before `prioritize()` call
+
+        LoadJobSet jobs_to_prioritize;
+
+        auto job_func = [&] (const LoadJobPtr & self)
+        {
+            auto pool_id = self->executionPool();
+            executing[pool_id]++;
+            if (executing[pool_id] > max_threads[0])
+                boosted = true;
+            ASSERT_LE(executing[pool_id], max_threads[pool_id]);
+
+            // Dynamic prioritization
+            if (--left == 0)
+            {
+                for (const auto & job : jobs_to_prioritize)
+                    t.loader.prioritize(job, 1);
+            }
+
+            t.randomSleepUs(100, 200, 100);
+
+            ASSERT_LE(executing[pool_id], max_threads[pool_id]);
+            executing[pool_id]--;
+        };
+
+        std::vector<LoadTaskPtr> tasks;
+        tasks.reserve(concurrency);
+        for (int i = 0; i < concurrency; i++)
+            tasks.push_back(makeLoadTask(t.loader, t.chainJobSet(jobs_in_chain, job_func)));
+        jobs_to_prioritize = getGoals(tasks); // All jobs
+        scheduleAndWaitLoadAll(tasks);
+
+        ASSERT_EQ(executing[0], 0);
+        ASSERT_EQ(executing[1], 0);
+        ASSERT_EQ(boosted, concurrency > 2);
+        boosted = false;
+    }
+
+}

src/Compression/CachedCompressedReadBuffer.cpp

@@ -28,7 +28,7 @@ void CachedCompressedReadBuffer::initInput()
 }
 
 
-void CachedCompressedReadBuffer::prefetch(int64_t priority)
+void CachedCompressedReadBuffer::prefetch(Priority priority)
 {
     initInput();
     file_in->prefetch(priority);

src/Compression/CachedCompressedReadBuffer.h

@@ -36,7 +36,7 @@ private:
 
     bool nextImpl() override;
 
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
     /// Passed into file_in.
     ReadBufferFromFileBase::ProfileCallback profile_callback;

src/Compression/CompressedReadBufferFromFile.cpp

@@ -51,7 +51,7 @@ CompressedReadBufferFromFile::CompressedReadBufferFromFile(std::unique_ptr<ReadB
 }
 
 
-void CompressedReadBufferFromFile::prefetch(int64_t priority)
+void CompressedReadBufferFromFile::prefetch(Priority priority)
 {
     file_in.prefetch(priority);
 }

src/Compression/CompressedReadBufferFromFile.h

@@ -43,7 +43,7 @@ private:
 
     bool nextImpl() override;
 
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
 public:
     explicit CompressedReadBufferFromFile(std::unique_ptr<ReadBufferFromFileBase> buf, bool allow_different_codecs_ = false);

src/Core/ServerSettings.h

@@ -63,7 +63,7 @@ namespace DB
     \
     M(Bool, disable_internal_dns_cache, false, "Disable internal DNS caching at all.", 0) \
     M(Int32, dns_cache_update_period, 15, "Internal DNS cache update period in seconds.", 0) \
-    M(UInt32, dns_max_consecutive_failures, 1024, "Max connection failures before dropping host from ClickHouse DNS cache.", 0) \
+    M(UInt32, dns_max_consecutive_failures, 1024, "Max DNS resolve failures of a hostname before dropping the hostname from ClickHouse DNS cache.", 0) \
     \
     M(UInt64, max_table_size_to_drop, 50000000000lu, "If size of a table is greater than this value (in bytes) than table could not be dropped with any DROP query.", 0) \
     M(UInt64, max_partition_size_to_drop, 50000000000lu, "Same as max_table_size_to_drop, but for the partitions.", 0) \

src/Disks/DiskEncrypted.cpp

@@ -138,19 +138,6 @@ namespace
         }
     }
 
-    String getCurrentKey(const String & path, const DiskEncryptedSettings & settings)
-    {
-        auto it = settings.keys.find(settings.current_key_id);
-        if (it == settings.keys.end())
-            throw Exception(
-                ErrorCodes::DATA_ENCRYPTION_ERROR,
-                "Not found a key with the current ID {} required to cipher file {}",
-                settings.current_key_id,
-                quoteString(path));
-
-        return it->second;
-    }
-
     String getKey(const String & path, const FileEncryption::Header & header, const DiskEncryptedSettings & settings)
     {
         auto it = settings.keys.find(header.key_id);
@@ -203,18 +190,19 @@ private:
 };
 
 DiskEncrypted::DiskEncrypted(
-    const String & name_, const Poco::Util::AbstractConfiguration & config_, const String & config_prefix_, const DisksMap & map_)
-    : DiskEncrypted(name_, parseDiskEncryptedSettings(name_, config_, config_prefix_, map_))
+    const String & name_, const Poco::Util::AbstractConfiguration & config_, const String & config_prefix_, const DisksMap & map_, bool use_fake_transaction_)
+    : DiskEncrypted(name_, parseDiskEncryptedSettings(name_, config_, config_prefix_, map_), use_fake_transaction_)
 {
 }
 
-DiskEncrypted::DiskEncrypted(const String & name_, std::unique_ptr<const DiskEncryptedSettings> settings_)
+DiskEncrypted::DiskEncrypted(const String & name_, std::unique_ptr<const DiskEncryptedSettings> settings_, bool use_fake_transaction_)
     : IDisk(name_)
     , delegate(settings_->wrapped_disk)
     , encrypted_name(name_)
     , disk_path(settings_->disk_path)
     , disk_absolute_path(settings_->wrapped_disk->getPath() + settings_->disk_path)
     , current_settings(std::move(settings_))
+    , use_fake_transaction(use_fake_transaction_)
 {
     delegate->createDirectories(disk_path);
 }
@@ -309,38 +297,6 @@ std::unique_ptr<ReadBufferFromFileBase> DiskEncrypted::readFile(
     return std::make_unique<ReadBufferFromEncryptedFile>(settings.local_fs_buffer_size, std::move(buffer), key, header);
 }
 
-std::unique_ptr<WriteBufferFromFileBase> DiskEncrypted::writeFile(const String & path, size_t buf_size, WriteMode mode, const WriteSettings &)
-{
-    auto wrapped_path = wrappedPath(path);
-    FileEncryption::Header header;
-    String key;
-    UInt64 old_file_size = 0;
-    auto settings = current_settings.get();
-    if (mode == WriteMode::Append && exists(path))
-    {
-        old_file_size = getFileSize(path);
-        if (old_file_size)
-        {
-            /// Append mode: we continue to use the same header.
-            auto read_buffer = delegate->readFile(wrapped_path, ReadSettings().adjustBufferSize(FileEncryption::Header::kSize));
-            header = readHeader(*read_buffer);
-            key = getKey(path, header, *settings);
-        }
-    }
-    if (!old_file_size)
-    {
-        /// Rewrite mode: we generate a new header.
-        key = getCurrentKey(path, *settings);
-        header.algorithm = settings->current_algorithm;
-        header.key_id = settings->current_key_id;
-        header.key_hash = calculateKeyHash(key);
-        header.init_vector = InitVector::random();
-    }
-    auto buffer = delegate->writeFile(wrapped_path, buf_size, mode);
-    return std::make_unique<WriteBufferFromEncryptedFile>(buf_size, std::move(buffer), key, header, old_file_size);
-}
-
-
 size_t DiskEncrypted::getFileSize(const String & path) const
 {
     auto wrapped_path = wrappedPath(path);
@@ -416,7 +372,7 @@ void registerDiskEncrypted(DiskFactory & factory, bool global_skip_access_check)
         const DisksMap & map) -> DiskPtr
     {
         bool skip_access_check = global_skip_access_check || config.getBool(config_prefix + ".skip_access_check", false);
-        DiskPtr disk = std::make_shared<DiskEncrypted>(name, config, config_prefix, map);
+        DiskPtr disk = std::make_shared<DiskEncrypted>(name, config, config_prefix, map, config.getBool(config_prefix + ".use_fake_transaction", true));
         disk->startup(context, skip_access_check);
         return disk;
     };

src/Disks/DiskEncrypted.h

@@ -6,22 +6,14 @@
 #include <Disks/IDisk.h>
 #include <Common/MultiVersion.h>
 #include <Disks/FakeDiskTransaction.h>
+#include <Disks/DiskEncryptedTransaction.h>
 
 
 namespace DB
 {
+
 class ReadBufferFromFileBase;
 class WriteBufferFromFileBase;
-namespace FileEncryption { enum class Algorithm; }
-
-struct DiskEncryptedSettings
-{
-    DiskPtr wrapped_disk;
-    String disk_path;
-    std::unordered_map<UInt64, String> keys;
-    UInt64 current_key_id;
-    FileEncryption::Algorithm current_algorithm;
-};
 
 /// Encrypted disk ciphers all written files on the fly and writes the encrypted files to an underlying (normal) disk.
 /// And when we read files from an encrypted disk it deciphers them automatically,
@@ -29,8 +21,8 @@ struct DiskEncryptedSettings
 class DiskEncrypted : public IDisk
 {
 public:
-    DiskEncrypted(const String & name_, const Poco::Util::AbstractConfiguration & config_, const String & config_prefix_, const DisksMap & map_);
-    DiskEncrypted(const String & name_, std::unique_ptr<const DiskEncryptedSettings> settings_);
+    DiskEncrypted(const String & name_, const Poco::Util::AbstractConfiguration & config_, const String & config_prefix_, const DisksMap & map_, bool use_fake_transaction_);
+    DiskEncrypted(const String & name_, std::unique_ptr<const DiskEncryptedSettings> settings_, bool use_fake_transaction_);
 
     const String & getName() const override { return encrypted_name; }
     const String & getPath() const override { return disk_absolute_path; }
@@ -59,28 +51,30 @@ public:
 
     void createDirectory(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->createDirectory(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->createDirectory(path);
+        tx->commit();
     }
 
     void createDirectories(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->createDirectories(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->createDirectories(path);
+        tx->commit();
     }
 
-
     void clearDirectory(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->clearDirectory(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->clearDirectory(path);
+        tx->commit();
     }
 
     void moveDirectory(const String & from_path, const String & to_path) override
     {
-        auto wrapped_from_path = wrappedPath(from_path);
-        auto wrapped_to_path = wrappedPath(to_path);
-        delegate->moveDirectory(wrapped_from_path, wrapped_to_path);
+        auto tx = createEncryptedTransaction();
+        tx->moveDirectory(from_path, to_path);
+        tx->commit();
     }
 
     DirectoryIteratorPtr iterateDirectory(const String & path) const override
@@ -91,22 +85,23 @@ public:
 
     void createFile(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->createFile(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->createFile(path);
+        tx->commit();
     }
 
     void moveFile(const String & from_path, const String & to_path) override
     {
-        auto wrapped_from_path = wrappedPath(from_path);
-        auto wrapped_to_path = wrappedPath(to_path);
-        delegate->moveFile(wrapped_from_path, wrapped_to_path);
+        auto tx = createEncryptedTransaction();
+        tx->moveFile(from_path, to_path);
+        tx->commit();
     }
 
     void replaceFile(const String & from_path, const String & to_path) override
     {
-        auto wrapped_from_path = wrappedPath(from_path);
-        auto wrapped_to_path = wrappedPath(to_path);
-        delegate->replaceFile(wrapped_from_path, wrapped_to_path);
+        auto tx = createEncryptedTransaction();
+        tx->replaceFile(from_path, to_path);
+        tx->commit();
     }
 
     void listFiles(const String & path, std::vector<String> & file_names) const override
@@ -129,61 +124,67 @@ public:
         const String & path,
         size_t buf_size,
         WriteMode mode,
-        const WriteSettings & settings) override;
+        const WriteSettings & settings) override
+    {
+        auto tx = createEncryptedTransaction();
+        auto result = tx->writeFile(path, buf_size, mode, settings);
+        return result;
+    }
 
     void removeFile(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeFile(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->removeFile(path);
+        tx->commit();
     }
 
     void removeFileIfExists(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeFileIfExists(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->removeFileIfExists(path);
+        tx->commit();
     }
 
     void removeDirectory(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeDirectory(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->removeDirectory(path);
+        tx->commit();
     }
 
     void removeRecursive(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeRecursive(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->removeRecursive(path);
+        tx->commit();
     }
 
     void removeSharedFile(const String & path, bool flag) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeSharedFile(wrapped_path, flag);
+        auto tx = createEncryptedTransaction();
+        tx->removeSharedFile(path, flag);
+        tx->commit();
     }
 
     void removeSharedRecursive(const String & path, bool keep_all_batch_data, const NameSet & file_names_remove_metadata_only) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeSharedRecursive(wrapped_path, keep_all_batch_data, file_names_remove_metadata_only);
+        auto tx = createEncryptedTransaction();
+        tx->removeSharedRecursive(path, keep_all_batch_data, file_names_remove_metadata_only);
+        tx->commit();
     }
 
     void removeSharedFiles(const RemoveBatchRequest & files, bool keep_all_batch_data, const NameSet & file_names_remove_metadata_only) override
     {
-        for (const auto & file : files)
-        {
-            auto wrapped_path = wrappedPath(file.path);
-            bool keep = keep_all_batch_data || file_names_remove_metadata_only.contains(fs::path(file.path).filename());
-            if (file.if_exists)
-                delegate->removeSharedFileIfExists(wrapped_path, keep);
-            else
-                delegate->removeSharedFile(wrapped_path, keep);
-        }
+        auto tx = createEncryptedTransaction();
+        tx->removeSharedFiles(files, keep_all_batch_data, file_names_remove_metadata_only);
+        tx->commit();
     }
 
     void removeSharedFileIfExists(const String & path, bool flag) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->removeSharedFileIfExists(wrapped_path, flag);
+        auto tx = createEncryptedTransaction();
+        tx->removeSharedFileIfExists(path, flag);
+        tx->commit();
     }
 
     Strings getBlobPath(const String & path) const override
@@ -194,8 +195,9 @@ public:
 
     void writeFileUsingBlobWritingFunction(const String & path, WriteMode mode, WriteBlobFunction && write_blob_function) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->writeFileUsingBlobWritingFunction(wrapped_path, mode, std::move(write_blob_function));
+        auto tx = createEncryptedTransaction();
+        tx->writeFileUsingBlobWritingFunction(path, mode, std::move(write_blob_function));
+        tx->commit();
     }
 
     std::unique_ptr<ReadBufferFromFileBase> readEncryptedFile(const String & path, const ReadSettings & settings) const override
@@ -210,8 +212,9 @@ public:
         WriteMode mode,
         const WriteSettings & settings) const override
     {
-        auto wrapped_path = wrappedPath(path);
-        return delegate->writeFile(wrapped_path, buf_size, mode, settings);
+        auto tx = createEncryptedTransaction();
+        auto buf = tx->writeEncryptedFile(path, buf_size, mode, settings);
+        return buf;
     }
 
     size_t getEncryptedFileSize(const String & path) const override
@@ -228,8 +231,9 @@ public:
 
     void setLastModified(const String & path, const Poco::Timestamp & timestamp) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->setLastModified(wrapped_path, timestamp);
+        auto tx = createEncryptedTransaction();
+        tx->setLastModified(path, timestamp);
+        tx->commit();
     }
 
     Poco::Timestamp getLastModified(const String & path) const override
@@ -246,15 +250,16 @@ public:
 
     void setReadOnly(const String & path) override
     {
-        auto wrapped_path = wrappedPath(path);
-        delegate->setReadOnly(wrapped_path);
+        auto tx = createEncryptedTransaction();
+        tx->setReadOnly(path);
+        tx->commit();
     }
 
     void createHardLink(const String & src_path, const String & dst_path) override
     {
-        auto wrapped_src_path = wrappedPath(src_path);
-        auto wrapped_dst_path = wrappedPath(dst_path);
-        delegate->createHardLink(wrapped_src_path, wrapped_dst_path);
+        auto tx = createEncryptedTransaction();
+        tx->createHardLink(src_path, dst_path);
+        tx->commit();
     }
 
     void truncateFile(const String & path, size_t size) override;
@@ -289,12 +294,23 @@ public:
 
     SyncGuardPtr getDirectorySyncGuard(const String & path) const override;
 
+    std::shared_ptr<DiskEncryptedTransaction> createEncryptedTransaction() const
+    {
+        auto delegate_transaction = delegate->createTransaction();
+        return std::make_shared<DiskEncryptedTransaction>(delegate_transaction, disk_path, *current_settings.get(), delegate.get());
+    }
+
     DiskTransactionPtr createTransaction() override
     {
-        /// Need to overwrite explicetly because this disk change
-        /// a lot of "delegate" methods.
+        if (use_fake_transaction)
+        {
             return std::make_shared<FakeDiskTransaction>(*this);
         }
+        else
+        {
+            return createEncryptedTransaction();
+        }
+    }
 
     UInt64 getTotalSpace() const override
     {
@@ -331,10 +347,7 @@ public:
 private:
     String wrappedPath(const String & path) const
     {
-        // if path starts_with disk_path -> got already wrapped path
-        if (!disk_path.empty() && path.starts_with(disk_path))
-            return path;
-        return disk_path + path;
+        return DiskEncryptedTransaction::wrappedPath(disk_path, path);
     }
 
     DiskPtr delegate;
@@ -342,6 +355,7 @@ private:
     const String disk_path;
     const String disk_absolute_path;
     MultiVersion<DiskEncryptedSettings> current_settings;
+    bool use_fake_transaction;
 };
 
 }

src/Disks/DiskEncryptedTransaction.cpp

@@ -0,0 +1,120 @@
+#include <Disks/DiskEncryptedTransaction.h>
+
+
+#if USE_SSL
+#include <IO/FileEncryptionCommon.h>
+#include <Common/Exception.h>
+#include <boost/algorithm/hex.hpp>
+#include <IO/ReadBufferFromEncryptedFile.h>
+#include <IO/ReadBufferFromFileDecorator.h>
+#include <IO/ReadBufferFromString.h>
+#include <IO/WriteBufferFromEncryptedFile.h>
+#include <Common/quoteString.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int DATA_ENCRYPTION_ERROR;
+}
+
+
+namespace
+{
+
+FileEncryption::Header readHeader(ReadBufferFromFileBase & read_buffer)
+{
+    try
+    {
+        FileEncryption::Header header;
+        header.read(read_buffer);
+        return header;
+    }
+    catch (Exception & e)
+    {
+        e.addMessage("While reading the header of encrypted file " + quoteString(read_buffer.getFileName()));
+        throw;
+    }
+}
+
+String getCurrentKey(const String & path, const DiskEncryptedSettings & settings)
+{
+    auto it = settings.keys.find(settings.current_key_id);
+    if (it == settings.keys.end())
+        throw Exception(
+            ErrorCodes::DATA_ENCRYPTION_ERROR,
+            "Not found a key with the current ID {} required to cipher file {}",
+            settings.current_key_id,
+            quoteString(path));
+
+    return it->second;
+}
+
+String getKey(const String & path, const FileEncryption::Header & header, const DiskEncryptedSettings & settings)
+{
+    auto it = settings.keys.find(header.key_id);
+    if (it == settings.keys.end())
+        throw Exception(
+            ErrorCodes::DATA_ENCRYPTION_ERROR,
+            "Not found a key with ID {} required to decipher file {}",
+            header.key_id,
+            quoteString(path));
+
+    String key = it->second;
+    if (FileEncryption::calculateKeyHash(key) != header.key_hash)
+        throw Exception(
+            ErrorCodes::DATA_ENCRYPTION_ERROR, "Wrong key with ID {}, could not decipher file {}", header.key_id, quoteString(path));
+
+    return key;
+}
+
+}
+
+void DiskEncryptedTransaction::copyFile(const std::string & from_file_path, const std::string & to_file_path)
+{
+    auto wrapped_from_path = wrappedPath(from_file_path);
+    auto wrapped_to_path = wrappedPath(to_file_path);
+    delegate_transaction->copyFile(wrapped_from_path, wrapped_to_path);
+}
+
+std::unique_ptr<WriteBufferFromFileBase> DiskEncryptedTransaction::writeFile( // NOLINT
+    const std::string & path,
+    size_t buf_size,
+    WriteMode mode,
+    const WriteSettings & settings,
+    bool autocommit)
+{
+    auto wrapped_path = wrappedPath(path);
+    FileEncryption::Header header;
+    String key;
+    UInt64 old_file_size = 0;
+    if (mode == WriteMode::Append && delegate_disk->exists(wrapped_path))
+    {
+        size_t size = delegate_disk->getFileSize(wrapped_path);
+        old_file_size = size > FileEncryption::Header::kSize ? (size - FileEncryption::Header::kSize) : 0;
+        if (old_file_size)
+        {
+            /// Append mode: we continue to use the same header.
+            auto read_buffer = delegate_disk->readFile(wrapped_path, ReadSettings().adjustBufferSize(FileEncryption::Header::kSize));
+            header = readHeader(*read_buffer);
+            key = getKey(path, header, current_settings);
+        }
+    }
+    if (!old_file_size)
+    {
+        /// Rewrite mode: we generate a new header.
+        key = getCurrentKey(path, current_settings);
+        header.algorithm = current_settings.current_algorithm;
+        header.key_id = current_settings.current_key_id;
+        header.key_hash = FileEncryption::calculateKeyHash(key);
+        header.init_vector = FileEncryption::InitVector::random();
+    }
+    auto buffer = delegate_transaction->writeFile(wrapped_path, buf_size, mode, settings, autocommit);
+    return std::make_unique<WriteBufferFromEncryptedFile>(buf_size, std::move(buffer), key, header, old_file_size);
+
+}
+
+}
+
+#endif

src/Disks/DiskEncryptedTransaction.h

@@ -0,0 +1,259 @@
+#pragma once
+
+#include "config.h"
+
+#if USE_SSL
+
+#include <Disks/IDiskTransaction.h>
+#include <Disks/IDisk.h>
+#include <IO/ReadBufferFromFile.h>
+#include <IO/WriteBufferFromFile.h>
+
+namespace DB
+{
+
+namespace FileEncryption { enum class Algorithm; }
+
+struct DiskEncryptedSettings
+{
+    DiskPtr wrapped_disk;
+    String disk_path;
+    std::unordered_map<UInt64, String> keys;
+    UInt64 current_key_id;
+    FileEncryption::Algorithm current_algorithm;
+};
+
+
+class DiskEncryptedTransaction : public IDiskTransaction
+{
+public:
+    static String wrappedPath(const String disk_path, const String & path)
+    {
+        // if path starts_with disk_path -> got already wrapped path
+        if (!disk_path.empty() && path.starts_with(disk_path))
+            return path;
+        return disk_path + path;
+    }
+
+    DiskEncryptedTransaction(DiskTransactionPtr delegate_transaction_, const std::string & disk_path_, DiskEncryptedSettings current_settings_, IDisk * delegate_disk_)
+        : delegate_transaction(delegate_transaction_)
+        , disk_path(disk_path_)
+        , current_settings(current_settings_)
+        , delegate_disk(delegate_disk_)
+    {}
+
+    /// Tries to commit all accumulated operations simultaneously.
+    /// If something fails rollback and throw exception.
+    void commit() override // NOLINT
+    {
+        delegate_transaction->commit();
+    }
+
+    void undo() override
+    {
+        delegate_transaction->undo();
+    }
+
+    ~DiskEncryptedTransaction() override = default;
+
+    /// Create directory.
+    void createDirectory(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->createDirectory(wrapped_path);
+    }
+
+    /// Create directory and all parent directories if necessary.
+    void createDirectories(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->createDirectories(wrapped_path);
+    }
+
+    /// Remove all files from the directory. Directories are not removed.
+    void clearDirectory(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->clearDirectory(wrapped_path);
+    }
+
+    /// Move directory from `from_path` to `to_path`.
+    void moveDirectory(const std::string & from_path, const std::string & to_path) override
+    {
+        auto wrapped_from_path = wrappedPath(from_path);
+        auto wrapped_to_path = wrappedPath(to_path);
+        delegate_transaction->moveDirectory(wrapped_from_path, wrapped_to_path);
+    }
+
+    void moveFile(const std::string & from_path, const std::string & to_path) override
+    {
+        auto wrapped_from_path = wrappedPath(from_path);
+        auto wrapped_to_path = wrappedPath(to_path);
+        delegate_transaction->moveFile(wrapped_from_path, wrapped_to_path);
+
+    }
+
+    void createFile(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->createFile(wrapped_path);
+    }
+
+    /// Move the file from `from_path` to `to_path`.
+    /// If a file with `to_path` path already exists, it will be replaced.
+    void replaceFile(const std::string & from_path, const std::string & to_path) override
+    {
+        auto wrapped_from_path = wrappedPath(from_path);
+        auto wrapped_to_path = wrappedPath(to_path);
+        delegate_transaction->replaceFile(wrapped_from_path, wrapped_to_path);
+    }
+
+    /// Only copy of several files supported now. Disk interface support copy to another disk
+    /// but it's impossible to implement correctly in transactions because other disk can
+    /// use different metadata storage.
+    /// TODO: maybe remove it at all, we don't want copies
+    void copyFile(const std::string & from_file_path, const std::string & to_file_path) override;
+
+    /// Open the file for write and return WriteBufferFromFileBase object.
+    std::unique_ptr<WriteBufferFromFileBase> writeFile( /// NOLINT
+        const std::string & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        WriteMode mode = WriteMode::Rewrite,
+        const WriteSettings & settings = {},
+        bool autocommit = true) override;
+
+    /// Remove file. Throws exception if file doesn't exists or it's a directory.
+    void removeFile(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeFile(wrapped_path);
+    }
+
+    /// Remove file if it exists.
+    void removeFileIfExists(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeFileIfExists(wrapped_path);
+    }
+
+    /// Remove directory. Throws exception if it's not a directory or if directory is not empty.
+    void removeDirectory(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeDirectory(wrapped_path);
+    }
+
+    /// Remove file or directory with all children. Use with extra caution. Throws exception if file doesn't exists.
+    void removeRecursive(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeRecursive(wrapped_path);
+    }
+
+    /// Remove file. Throws exception if file doesn't exists or if directory is not empty.
+    /// Differs from removeFile for S3/HDFS disks
+    /// Second bool param is a flag to remove (true) or keep (false) shared data on S3
+    void removeSharedFile(const std::string & path, bool keep_shared_data) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeSharedFile(wrapped_path, keep_shared_data);
+    }
+
+    /// Remove file or directory with all children. Use with extra caution. Throws exception if file doesn't exists.
+    /// Differs from removeRecursive for S3/HDFS disks
+    /// Second bool param is a flag to remove (false) or keep (true) shared data on S3.
+    /// Third param determines which files cannot be removed even if second is true.
+    void removeSharedRecursive(const std::string & path, bool keep_all_shared_data, const NameSet & file_names_remove_metadata_only) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeSharedRecursive(wrapped_path, keep_all_shared_data, file_names_remove_metadata_only);
+    }
+
+    /// Remove file or directory if it exists.
+    /// Differs from removeFileIfExists for S3/HDFS disks
+    /// Second bool param is a flag to remove (true) or keep (false) shared data on S3
+    void removeSharedFileIfExists(const std::string & path, bool keep_shared_data) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->removeSharedFileIfExists(wrapped_path, keep_shared_data);
+    }
+
+    /// Batch request to remove multiple files.
+    /// May be much faster for blob storage.
+    /// Second bool param is a flag to remove (true) or keep (false) shared data on S3.
+    /// Third param determines which files cannot be removed even if second is true.
+    void removeSharedFiles(const RemoveBatchRequest & files, bool keep_all_batch_data, const NameSet & file_names_remove_metadata_only) override
+    {
+        for (const auto & file : files)
+        {
+            auto wrapped_path = wrappedPath(file.path);
+            bool keep = keep_all_batch_data || file_names_remove_metadata_only.contains(fs::path(file.path).filename());
+            if (file.if_exists)
+                delegate_transaction->removeSharedFileIfExists(wrapped_path, keep);
+            else
+                delegate_transaction->removeSharedFile(wrapped_path, keep);
+        }
+    }
+
+    /// Set last modified time to file or directory at `path`.
+    void setLastModified(const std::string & path, const Poco::Timestamp & timestamp) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->setLastModified(wrapped_path, timestamp);
+    }
+
+    /// Just chmod.
+    void chmod(const String & path, mode_t mode) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->chmod(wrapped_path, mode);
+    }
+
+    /// Set file at `path` as read-only.
+    void setReadOnly(const std::string & path) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->setReadOnly(wrapped_path);
+    }
+
+    /// Create hardlink from `src_path` to `dst_path`.
+    void createHardLink(const std::string & src_path, const std::string & dst_path) override
+    {
+        auto wrapped_src_path = wrappedPath(src_path);
+        auto wrapped_dst_path = wrappedPath(dst_path);
+        delegate_transaction->createHardLink(wrapped_src_path, wrapped_dst_path);
+    }
+
+    void writeFileUsingBlobWritingFunction(const String & path, WriteMode mode, WriteBlobFunction && write_blob_function) override
+    {
+        auto wrapped_path = wrappedPath(path);
+        delegate_transaction->writeFileUsingBlobWritingFunction(wrapped_path, mode, std::move(write_blob_function));
+    }
+
+    std::unique_ptr<WriteBufferFromFileBase> writeEncryptedFile(
+        const String & path,
+        size_t buf_size,
+        WriteMode mode,
+        const WriteSettings & settings) const
+    {
+        auto wrapped_path = wrappedPath(path);
+        return delegate_transaction->writeFile(wrapped_path, buf_size, mode, settings);
+    }
+
+
+private:
+
+    String wrappedPath(const String & path) const
+    {
+        return wrappedPath(disk_path, path);
+    }
+
+    DiskTransactionPtr delegate_transaction;
+    std::string disk_path;
+    DiskEncryptedSettings current_settings;
+    IDisk * delegate_disk;
+};
+
+}
+
+#endif

src/Disks/IO/AsynchronousBoundedReadBuffer.cpp

@@ -83,19 +83,19 @@ bool AsynchronousBoundedReadBuffer::hasPendingDataToRead()
 }
 
 std::future<IAsynchronousReader::Result>
-AsynchronousBoundedReadBuffer::asyncReadInto(char * data, size_t size, int64_t priority)
+AsynchronousBoundedReadBuffer::asyncReadInto(char * data, size_t size, Priority priority)
 {
     IAsynchronousReader::Request request;
     request.descriptor = std::make_shared<RemoteFSFileDescriptor>(*impl, async_read_counters);
     request.buf = data;
     request.size = size;
     request.offset = file_offset_of_buffer_end;
-    request.priority = read_settings.priority + priority;
+    request.priority = Priority{read_settings.priority.value + priority.value};
     request.ignore = bytes_to_ignore;
     return reader.submit(request);
 }
 
-void AsynchronousBoundedReadBuffer::prefetch(int64_t priority)
+void AsynchronousBoundedReadBuffer::prefetch(Priority priority)
 {
     if (prefetch_future.valid())
         return;

src/Disks/IO/AsynchronousBoundedReadBuffer.h

@@ -39,7 +39,7 @@ public:
 
     off_t seek(off_t offset_, int whence) override;
 
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
     void setReadUntilPosition(size_t position) override; /// [..., position).
 
@@ -72,7 +72,7 @@ private:
     struct LastPrefetchInfo
     {
         UInt64 submit_time = 0;
-        size_t priority = 0;
+        Priority priority;
     };
     LastPrefetchInfo last_prefetch_info;
 
@@ -87,7 +87,7 @@ private:
         int64_t size,
         const std::unique_ptr<Stopwatch> & execution_watch);
 
-    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, int64_t priority);
+    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, Priority priority);
 
     void resetPrefetch(FilesystemPrefetchState state);
 

src/Disks/tests/gtest_disk_encrypted.cpp

@@ -40,7 +40,7 @@ protected:
         settings->keys[0] = key;
         settings->current_key_id = 0;
         settings->disk_path = path;
-        encrypted_disk = std::make_shared<DiskEncrypted>("encrypted_disk", std::move(settings));
+        encrypted_disk = std::make_shared<DiskEncrypted>("encrypted_disk", std::move(settings), true);
     }
 
     String getFileNames()

src/Functions/repeat.cpp

@@ -13,7 +13,6 @@ namespace DB
 namespace ErrorCodes
 {
     extern const int ILLEGAL_COLUMN;
-    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
     extern const int TOO_LARGE_STRING_SIZE;
 }
 
@@ -25,18 +24,16 @@ struct RepeatImpl
     /// Safety threshold against DoS.
     static inline void checkRepeatTime(UInt64 repeat_time)
     {
-        static constexpr UInt64 max_repeat_times = 1000000;
+        static constexpr UInt64 max_repeat_times = 1'000'000;
         if (repeat_time > max_repeat_times)
-            throw Exception(ErrorCodes::TOO_LARGE_STRING_SIZE, "Too many times to repeat ({}), maximum is: {}",
-                std::to_string(repeat_time), std::to_string(max_repeat_times));
+            throw Exception(ErrorCodes::TOO_LARGE_STRING_SIZE, "Too many times to repeat ({}), maximum is: {}", repeat_time, max_repeat_times);
     }
 
     static inline void checkStringSize(UInt64 size)
     {
         static constexpr UInt64 max_string_size = 1 << 30;
         if (size > max_string_size)
-            throw Exception(ErrorCodes::TOO_LARGE_STRING_SIZE, "Too large string size ({}) in function repeat, maximum is: {}",
-                size, max_string_size);
+            throw Exception(ErrorCodes::TOO_LARGE_STRING_SIZE, "Too large string size ({}) in function repeat, maximum is: {}", size, max_string_size);
     }
 
     template <typename T>
@@ -186,36 +183,37 @@ public:
 
     bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
 
-    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
     {
-        if (!isString(arguments[0]))
-            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}",
-                arguments[0]->getName(), getName());
-        if (!isInteger(arguments[1]))
-            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}",
-                arguments[1]->getName(), getName());
-        return arguments[0];
+        FunctionArgumentDescriptors args{
+            {"s", &isString<IDataType>, nullptr, "String"},
+            {"n", &isInteger<IDataType>, nullptr, "Integer"},
+        };
+
+        validateFunctionArgumentTypes(*this, arguments, args);
+
+        return std::make_shared<DataTypeString>();
     }
 
     bool useDefaultImplementationForConstants() const override { return true; }
 
-    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t) const override
+    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & /*result_type*/, size_t /*input_rows_count*/) const override
     {
-        const auto & strcolumn = arguments[0].column;
-        const auto & numcolumn = arguments[1].column;
+        const auto & col_str = arguments[0].column;
+        const auto & col_num = arguments[1].column;
         ColumnPtr res;
 
-        if (const ColumnString * col = checkAndGetColumn<ColumnString>(strcolumn.get()))
+        if (const ColumnString * col = checkAndGetColumn<ColumnString>(col_str.get()))
         {
-            if (const ColumnConst * scale_column_num = checkAndGetColumn<ColumnConst>(numcolumn.get()))
+            if (const ColumnConst * col_num_const = checkAndGetColumn<ColumnConst>(col_num.get()))
             {
                 auto col_res = ColumnString::create();
                 castType(arguments[1].type.get(), [&](const auto & type)
                 {
                     using DataType = std::decay_t<decltype(type)>;
                     using T = typename DataType::FieldType;
-                    T repeat_time = scale_column_num->getValue<T>();
-                    RepeatImpl::vectorStrConstRepeat(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets(), repeat_time);
+                    T times = col_num_const->getValue<T>();
+                    RepeatImpl::vectorStrConstRepeat(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets(), times);
                     return true;
                 });
                 return col_res;
@@ -224,9 +222,9 @@ public:
                 {
                     using DataType = std::decay_t<decltype(type)>;
                     using T = typename DataType::FieldType;
-                    const ColumnVector<T> * colnum = checkAndGetColumn<ColumnVector<T>>(numcolumn.get());
+                    const ColumnVector<T> * column = checkAndGetColumn<ColumnVector<T>>(col_num.get());
                     auto col_res = ColumnString::create();
-                    RepeatImpl::vectorStrVectorRepeat(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets(), colnum->getData());
+                    RepeatImpl::vectorStrVectorRepeat(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets(), column->getData());
                     res = std::move(col_res);
                     return true;
                 }))
@@ -234,7 +232,7 @@ public:
                 return res;
             }
         }
-        else if (const ColumnConst * col_const = checkAndGetColumn<ColumnConst>(strcolumn.get()))
+        else if (const ColumnConst * col_const = checkAndGetColumn<ColumnConst>(col_str.get()))
         {
             /// Note that const-const case is handled by useDefaultImplementationForConstants.
 
@@ -244,9 +242,9 @@ public:
                 {
                     using DataType = std::decay_t<decltype(type)>;
                     using T = typename DataType::FieldType;
-                    const ColumnVector<T> * colnum = checkAndGetColumn<ColumnVector<T>>(numcolumn.get());
+                    const ColumnVector<T> * column = checkAndGetColumn<ColumnVector<T>>(col_num.get());
                     auto col_res = ColumnString::create();
-                    RepeatImpl::constStrVectorRepeat(copy_str, col_res->getChars(), col_res->getOffsets(), colnum->getData());
+                    RepeatImpl::constStrVectorRepeat(copy_str, col_res->getChars(), col_res->getOffsets(), column->getData());
                     res = std::move(col_res);
                     return true;
                 }))

src/Functions/space.cpp

@@ -0,0 +1,179 @@
+#include <Columns/ColumnString.h>
+#include <Columns/ColumnsNumber.h>
+#include <DataTypes/DataTypesNumber.h>
+#include <DataTypes/DataTypeString.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionHelpers.h>
+#include <Functions/IFunction.h>
+#include <cstring>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_COLUMN;
+    extern const int TOO_LARGE_STRING_SIZE;
+}
+
+namespace
+{
+
+/// Prints whitespace n-times. Actually, space() could also be pushed down to repeat(). Chose a standalone-implementation because
+/// we can do memset() whereas repeat() does memcpy().
+class FunctionSpace : public IFunction
+{
+private:
+    static constexpr auto space = ' ';
+
+    /// Safety threshold against DoS.
+    static inline void checkRepeatTime(size_t repeat_time)
+    {
+        static constexpr auto max_repeat_times = 1'000'000uz;
+        if (repeat_time > max_repeat_times)
+            throw Exception(ErrorCodes::TOO_LARGE_STRING_SIZE, "Too many times to repeat ({}), maximum is: {}", repeat_time, max_repeat_times);
+    }
+
+public:
+    static constexpr auto name = "space";
+    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionSpace>(); }
+
+    String getName() const override { return name; }
+    size_t getNumberOfArguments() const override { return 1; }
+    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
+
+    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
+    {
+        FunctionArgumentDescriptors args{
+            {"n", &isInteger<IDataType>, nullptr, "Integer"}
+        };
+
+        validateFunctionArgumentTypes(*this, arguments, args);
+
+        return std::make_shared<DataTypeString>();
+    }
+
+
+    template <typename DataType>
+    bool executeConstant(ColumnPtr col_times, ColumnString::Offsets & res_offsets, ColumnString::Chars & res_chars) const
+    {
+        const ColumnConst * col_times_const = checkAndGetColumn<ColumnConst>(col_times.get());
+
+        const ColumnPtr & col_times_const_internal = col_times_const->getDataColumnPtr();
+        if (!checkAndGetColumn<typename DataType::ColumnType>(col_times_const_internal.get()))
+            return false;
+
+        using T = typename DataType::FieldType;
+        T times = col_times_const->getValue<T>();
+
+        if (times < 1)
+            times = 0;
+
+        checkRepeatTime(times);
+
+        res_offsets.resize(col_times->size());
+        res_chars.resize(col_times->size() * (times + 1));
+
+        size_t pos = 0;
+
+        for (size_t i = 0; i < col_times->size(); ++i)
+        {
+            memset(res_chars.begin() + pos, space, times);
+            pos += times;
+
+            *(res_chars.begin() + pos) = '\0';
+            pos += 1;
+
+            res_offsets[i] = pos;
+        }
+
+        return true;
+    }
+
+
+    template <typename DataType>
+    bool executeVector(ColumnPtr col_times_, ColumnString::Offsets & res_offsets, ColumnString::Chars & res_chars) const
+    {
+        auto * col_times = checkAndGetColumn<typename DataType::ColumnType>(col_times_.get());
+        if (!col_times)
+            return false;
+
+        res_offsets.resize(col_times->size());
+        res_chars.resize(col_times->size() * 10); /// heuristic
+
+        const PaddedPODArray<typename DataType::FieldType> & times_data = col_times->getData();
+
+        size_t pos = 0;
+
+        for (size_t i = 0; i < col_times->size(); ++i)
+        {
+            typename DataType::FieldType times = times_data[i];
+
+            if (times < 1)
+                times = 0;
+
+            checkRepeatTime(times);
+
+            if (pos + times + 1 > res_chars.size())
+                res_chars.resize(std::max(2 * res_chars.size(), static_cast<size_t>(pos + times + 1)));
+
+            memset(res_chars.begin() + pos, space, times);
+            pos += times;
+
+            *(res_chars.begin() + pos) = '\0';
+            pos += 1;
+
+            res_offsets[i] = pos;
+        }
+
+        res_chars.resize(pos);
+
+        return true;
+    }
+
+
+    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
+    {
+        const auto & col_num = arguments[0].column;
+
+        auto col_res = ColumnString::create();
+
+        ColumnString::Offsets & res_offsets = col_res->getOffsets();
+        ColumnString::Chars & res_chars = col_res->getChars();
+
+        if (const ColumnConst * col_num_const = checkAndGetColumn<ColumnConst>(col_num.get()))
+        {
+            if ((executeConstant<DataTypeUInt8>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeUInt16>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeUInt32>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeUInt64>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeInt8>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeInt16>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeInt32>(col_num, res_offsets, res_chars))
+                || (executeConstant<DataTypeInt64>(col_num, res_offsets, res_chars)))
+                return col_res;
+        }
+        else
+        {
+            if ((executeVector<DataTypeUInt8>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeUInt16>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeUInt32>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeUInt64>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeInt8>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeInt16>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeInt32>(col_num, res_offsets, res_chars))
+                || (executeVector<DataTypeInt64>(col_num, res_offsets, res_chars)))
+                return col_res;
+        }
+
+        throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Illegal column {} of argument of function {}", arguments[0].column->getName(), getName());
+    }
+};
+}
+
+REGISTER_FUNCTION(Space)
+{
+    factory.registerFunction<FunctionSpace>({}, FunctionFactory::CaseInsensitive);
+}
+
+}

src/IO/AsynchronousReadBufferFromFile.cpp

@@ -26,7 +26,7 @@ namespace ErrorCodes
 
 AsynchronousReadBufferFromFile::AsynchronousReadBufferFromFile(
     IAsynchronousReader & reader_,
-    Int32 priority_,
+    Priority priority_,
     const std::string & file_name_,
     size_t buf_size,
     int flags,
@@ -60,7 +60,7 @@ AsynchronousReadBufferFromFile::AsynchronousReadBufferFromFile(
 
 AsynchronousReadBufferFromFile::AsynchronousReadBufferFromFile(
     IAsynchronousReader & reader_,
-    Int32 priority_,
+    Priority priority_,
     int & fd_,
     const std::string & original_file_name,
     size_t buf_size,

src/IO/AsynchronousReadBufferFromFile.h

@@ -17,7 +17,7 @@ protected:
 public:
     explicit AsynchronousReadBufferFromFile(
         IAsynchronousReader & reader_,
-        Int32 priority_,
+        Priority priority_,
         const std::string & file_name_,
         size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
         int flags = -1,
@@ -28,7 +28,7 @@ public:
     /// Use pre-opened file descriptor.
     explicit AsynchronousReadBufferFromFile(
         IAsynchronousReader & reader_,
-        Int32 priority_,
+        Priority priority_,
         int & fd, /// Will be set to -1 if constructor didn't throw and ownership of file descriptor is passed to the object.
         const std::string & original_file_name = {},
         size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
@@ -58,7 +58,7 @@ private:
 public:
     AsynchronousReadBufferFromFileWithDescriptorsCache(
         IAsynchronousReader & reader_,
-        Int32 priority_,
+        Priority priority_,
         const std::string & file_name_,
         size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
         int flags = -1,

src/IO/AsynchronousReadBufferFromFileDescriptor.cpp

@@ -40,14 +40,14 @@ std::string AsynchronousReadBufferFromFileDescriptor::getFileName() const
 }
 
 
-std::future<IAsynchronousReader::Result> AsynchronousReadBufferFromFileDescriptor::asyncReadInto(char * data, size_t size, int64_t priority)
+std::future<IAsynchronousReader::Result> AsynchronousReadBufferFromFileDescriptor::asyncReadInto(char * data, size_t size, Priority priority)
 {
     IAsynchronousReader::Request request;
     request.descriptor = std::make_shared<IAsynchronousReader::LocalFileDescriptor>(fd);
     request.buf = data;
     request.size = size;
     request.offset = file_offset_of_buffer_end;
-    request.priority = base_priority + priority;
+    request.priority = Priority{base_priority.value + priority.value};
     request.ignore = bytes_to_ignore;
     bytes_to_ignore = 0;
 
@@ -61,7 +61,7 @@ std::future<IAsynchronousReader::Result> AsynchronousReadBufferFromFileDescripto
 }
 
 
-void AsynchronousReadBufferFromFileDescriptor::prefetch(int64_t priority)
+void AsynchronousReadBufferFromFileDescriptor::prefetch(Priority priority)
 {
     if (prefetch_future.valid())
         return;
@@ -151,7 +151,7 @@ void AsynchronousReadBufferFromFileDescriptor::finalize()
 
 AsynchronousReadBufferFromFileDescriptor::AsynchronousReadBufferFromFileDescriptor(
     IAsynchronousReader & reader_,
-    Int32 priority_,
+    Priority priority_,
     int fd_,
     size_t buf_size,
     char * existing_memory,

src/IO/AsynchronousReadBufferFromFileDescriptor.h

@@ -4,6 +4,7 @@
 #include <IO/AsynchronousReader.h>
 #include <Interpreters/Context.h>
 #include <Common/Throttler_fwd.h>
+#include <Common/Priority.h>
 
 #include <optional>
 #include <unistd.h>
@@ -18,7 +19,7 @@ class AsynchronousReadBufferFromFileDescriptor : public ReadBufferFromFileBase
 {
 protected:
     IAsynchronousReader & reader;
-    int64_t base_priority;
+    Priority base_priority;
 
     Memory<> prefetch_buffer;
     std::future<IAsynchronousReader::Result> prefetch_future;
@@ -39,7 +40,7 @@ protected:
 public:
     AsynchronousReadBufferFromFileDescriptor(
         IAsynchronousReader & reader_,
-        Int32 priority_,
+        Priority priority_,
         int fd_,
         size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
         char * existing_memory = nullptr,
@@ -49,7 +50,7 @@ public:
 
     ~AsynchronousReadBufferFromFileDescriptor() override;
 
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
     int getFD() const
     {
@@ -70,7 +71,7 @@ public:
     size_t getFileSize() override;
 
 private:
-    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, int64_t priority);
+    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, Priority priority);
 };
 
 }

src/IO/AsynchronousReader.h

@@ -6,6 +6,7 @@
 #include <future>
 #include <boost/noncopyable.hpp>
 #include <Common/Stopwatch.h>
+#include <Common/Priority.h>
 
 
 namespace DB
@@ -47,7 +48,7 @@ public:
         size_t offset = 0;
         size_t size = 0;
         char * buf = nullptr;
-        int64_t priority = 0;
+        Priority priority;
         size_t ignore = 0;
     };
 

src/IO/CompressedReadBufferWrapper.h

@@ -19,7 +19,7 @@ public:
     const ReadBuffer & getWrappedReadBuffer() const { return *in; }
     ReadBuffer & getWrappedReadBuffer() { return *in; }
 
-    void prefetch(int64_t priority) override { in->prefetch(priority); }
+    void prefetch(Priority priority) override { in->prefetch(priority); }
 
 protected:
     std::unique_ptr<ReadBuffer> in;

src/IO/ParallelReadBuffer.cpp

@@ -87,7 +87,7 @@ bool ParallelReadBuffer::addReaderToPool()
     auto worker = read_workers.emplace_back(std::make_shared<ReadWorker>(std::move(reader), range_start, size));
 
     ++active_working_reader;
-    schedule([this, my_worker = std::move(worker)]() mutable { readerThreadFunction(std::move(my_worker)); }, 0);
+    schedule([this, my_worker = std::move(worker)]() mutable { readerThreadFunction(std::move(my_worker)); }, Priority{});
 
     return true;
 }

src/IO/PeekableReadBuffer.h

@@ -20,7 +20,7 @@ public:
 
     ~PeekableReadBuffer() override;
 
-    void prefetch(int64_t priority) override { sub_buf->prefetch(priority); }
+    void prefetch(Priority priority) override { sub_buf->prefetch(priority); }
 
     /// Sets checkpoint at current position
     ALWAYS_INLINE inline void setCheckpoint()

src/IO/ReadBuffer.h

@@ -6,6 +6,7 @@
 #include <memory>
 
 #include <Common/Exception.h>
+#include <Common/Priority.h>
 #include <IO/BufferBase.h>
 #include <IO/AsynchronousReader.h>
 
@@ -20,7 +21,7 @@ namespace ErrorCodes
     extern const int NOT_IMPLEMENTED;
 }
 
-static constexpr auto DEFAULT_PREFETCH_PRIORITY = 0;
+static constexpr auto DEFAULT_PREFETCH_PRIORITY = Priority{0};
 
 /** A simple abstract class for buffered data reading (char sequences) from somewhere.
   * Unlike std::istream, it provides access to the internal buffer,
@@ -208,10 +209,10 @@ public:
 
     /** Do something to allow faster subsequent call to 'nextImpl' if possible.
       * It's used for asynchronous readers with double-buffering.
-      * `priority` is the Threadpool priority, with which the prefetch task will be schedules.
-      * Smaller is more priority.
+      * `priority` is the `ThreadPool` priority, with which the prefetch task will be scheduled.
+      * Lower value means higher priority.
       */
-    virtual void prefetch(int64_t /* priority */) {}
+    virtual void prefetch(Priority) {}
 
     /**
      * Set upper bound for read range [..., position).

src/IO/ReadBufferFromFileDescriptor.cpp

@@ -124,7 +124,7 @@ bool ReadBufferFromFileDescriptor::nextImpl()
 }
 
 
-void ReadBufferFromFileDescriptor::prefetch(int64_t)
+void ReadBufferFromFileDescriptor::prefetch(Priority)
 {
 #if defined(POSIX_FADV_WILLNEED)
     /// For direct IO, loading data into page cache is pointless.

src/IO/ReadBufferFromFileDescriptor.h

@@ -25,7 +25,7 @@ protected:
     ThrottlerPtr throttler;
 
     bool nextImpl() override;
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
     /// Name or some description of file.
     std::string getFileName() const override;

src/IO/ReadBufferFromMemory.cpp

@@ -12,7 +12,7 @@ off_t ReadBufferFromMemory::seek(off_t offset, int whence)
 {
     if (whence == SEEK_SET)
     {
-        if (offset >= 0 && internal_buffer.begin() + offset < internal_buffer.end())
+        if (offset >= 0 && internal_buffer.begin() + offset <= internal_buffer.end())
         {
             pos = internal_buffer.begin() + offset;
             working_buffer = internal_buffer; /// We need to restore `working_buffer` in case the position was at EOF before this seek().
@@ -25,7 +25,7 @@ off_t ReadBufferFromMemory::seek(off_t offset, int whence)
     else if (whence == SEEK_CUR)
     {
         Position new_pos = pos + offset;
-        if (new_pos >= internal_buffer.begin() && new_pos < internal_buffer.end())
+        if (new_pos >= internal_buffer.begin() && new_pos <= internal_buffer.end())
         {
             pos = new_pos;
             working_buffer = internal_buffer; /// We need to restore `working_buffer` in case the position was at EOF before this seek().

src/IO/ReadSettings.h

@@ -5,6 +5,7 @@
 #include <Core/Defines.h>
 #include <Interpreters/Cache/FileCache_fwd.h>
 #include <Common/Throttler_fwd.h>
+#include <Common/Priority.h>
 #include <IO/ResourceLink.h>
 
 namespace DB
@@ -84,8 +85,8 @@ struct ReadSettings
     size_t mmap_threshold = 0;
     MMappedFileCache * mmap_cache = nullptr;
 
-    /// For 'pread_threadpool'/'io_uring' method. Lower is more priority.
-    size_t priority = 0;
+    /// For 'pread_threadpool'/'io_uring' method. Lower value is higher priority.
+    Priority priority;
 
     bool load_marks_asynchronously = true;
 

src/IO/S3/copyS3File.cpp

@@ -361,7 +361,7 @@ namespace
                             task->exception = std::current_exception();
                         }
                         task_finish_notify();
-                    }, 0);
+                    }, Priority{});
                 }
                 catch (...)
                 {

src/IO/SeekAvoidingReadBuffer.h

@@ -17,7 +17,7 @@ public:
 
     off_t seek(off_t off, int whence) override;
 
-    void prefetch(int64_t priority) override { impl->prefetch(priority); }
+    void prefetch(Priority priority) override { impl->prefetch(priority); }
 
 private:
     UInt64 min_bytes_for_seek; /// Minimum positive seek offset which shall be executed using seek operation.

src/IO/WriteBufferFromS3TaskTracker.cpp

@@ -113,7 +113,7 @@ void WriteBufferFromS3::TaskTracker::add(Callback && func)
 {
     LOG_TEST(log, "add, in queue {}", futures.size());
 
-    auto future = scheduler(std::move(func), 0);
+    auto future = scheduler(std::move(func), Priority{});
     auto exit_scope = scope_guard(
         [&future]()
         {

src/Interpreters/Context.cpp

@@ -4269,7 +4269,7 @@ ReadSettings Context::getReadSettings() const
     res.prefetch_buffer_size = settings.prefetch_buffer_size;
     res.direct_io_threshold = settings.min_bytes_to_use_direct_io;
     res.mmap_threshold = settings.min_bytes_to_use_mmap_io;
-    res.priority = settings.read_priority;
+    res.priority = Priority{settings.read_priority};
 
     res.remote_throttler = getRemoteReadThrottler();
     res.local_throttler = getLocalReadThrottler();

src/Interpreters/ExpressionAnalyzer.cpp

@@ -969,6 +969,15 @@ const ASTSelectQuery * ExpressionAnalyzer::getSelectQuery() const
     return select_query;
 }
 
+bool ExpressionAnalyzer::isRemoteStorage() const
+{
+    const Settings & csettings = getContext()->getSettingsRef();
+    // Consider any storage used in parallel replicas as remote, so the query is executed in multiple servers
+    const bool enable_parallel_processing_of_joins
+        = csettings.max_parallel_replicas > 1 && csettings.allow_experimental_parallel_reading_from_replicas > 0;
+    return syntax->is_remote_storage || enable_parallel_processing_of_joins;
+}
+
 const ASTSelectQuery * SelectQueryExpressionAnalyzer::getAggregatingQuery() const
 {
     if (!has_aggregation)

src/Interpreters/ExpressionAnalyzer.h

@@ -201,7 +201,7 @@ protected:
 
     const ASTSelectQuery * getSelectQuery() const;
 
-    bool isRemoteStorage() const { return syntax->is_remote_storage; }
+    bool isRemoteStorage() const;
 
     NamesAndTypesList getColumnsAfterArrayJoin(ActionsDAGPtr & actions, const NamesAndTypesList & src_columns);
     NamesAndTypesList analyzeJoin(ActionsDAGPtr & actions, const NamesAndTypesList & src_columns);

src/Interpreters/FilesystemReadPrefetchesLog.cpp

@@ -19,7 +19,7 @@ NamesAndTypesList FilesystemReadPrefetchesLogElement::getNamesAndTypes()
         {"offset", std::make_shared<DataTypeUInt64>()},
         {"size", std::make_shared<DataTypeInt64>()},
         {"prefetch_submit_time", std::make_shared<DataTypeDateTime64>(6)},
-        {"priority", std::make_shared<DataTypeUInt64>()},
+        {"priority", std::make_shared<DataTypeInt64>()},
         {"prefetch_execution_start_time", std::make_shared<DataTypeDateTime64>(6)},
         {"prefetch_execution_end_time", std::make_shared<DataTypeDateTime64>(6)},
         {"prefetch_execution_time_us", std::make_shared<DataTypeUInt64>()},
@@ -40,7 +40,7 @@ void FilesystemReadPrefetchesLogElement::appendToBlock(MutableColumns & columns)
     columns[i++]->insert(offset);
     columns[i++]->insert(size);
     columns[i++]->insert(prefetch_submit_time);
-    columns[i++]->insert(priority);
+    columns[i++]->insert(priority.value);
     if (execution_watch)
     {
         columns[i++]->insert(execution_watch->getStart());

src/Interpreters/FilesystemReadPrefetchesLog.h

@@ -4,6 +4,7 @@
 #include <Core/NamesAndTypes.h>
 #include <Interpreters/SystemLog.h>
 #include <Common/Stopwatch.h>
+#include <Common/Priority.h>
 
 namespace DB
 {
@@ -25,7 +26,7 @@ struct FilesystemReadPrefetchesLogElement
     Int64 size; /// -1 means unknown
     Decimal64 prefetch_submit_time{};
     std::optional<Stopwatch> execution_watch;
-    size_t priority;
+    Priority priority;
     FilesystemPrefetchState state;
     UInt64 thread_id;
     String reader_id;

src/Interpreters/GlobalSubqueriesVisitor.h

@@ -205,10 +205,19 @@ public:
     }
 
 private:
+    static bool shouldBeExecutedGlobally(const Data & data)
+    {
+        const Settings & settings = data.getContext()->getSettingsRef();
+        /// For parallel replicas we reinterpret JOIN as GLOBAL JOIN as a way to broadcast data
+        const bool enable_parallel_processing_of_joins = data.getContext()->canUseParallelReplicasOnInitiator();
+        return settings.prefer_global_in_and_join || enable_parallel_processing_of_joins;
+    }
+
+
     /// GLOBAL IN
     static void visit(ASTFunction & func, ASTPtr &, Data & data)
     {
-        if ((data.getContext()->getSettingsRef().prefer_global_in_and_join
+        if ((shouldBeExecutedGlobally(data)
              && (func.name == "in" || func.name == "notIn" || func.name == "nullIn" || func.name == "notNullIn"))
             || func.name == "globalIn" || func.name == "globalNotIn" || func.name == "globalNullIn" || func.name == "globalNotNullIn")
         {
@@ -238,8 +247,7 @@ private:
     static void visit(ASTTablesInSelectQueryElement & table_elem, ASTPtr &, Data & data)
     {
         if (table_elem.table_join
-            && (table_elem.table_join->as<ASTTableJoin &>().locality == JoinLocality::Global
-                || data.getContext()->getSettingsRef().prefer_global_in_and_join))
+            && (table_elem.table_join->as<ASTTableJoin &>().locality == JoinLocality::Global || shouldBeExecutedGlobally(data)))
         {
             data.addExternalStorage(table_elem.table_expression, true);
             data.has_global_subqueries = true;

src/Interpreters/InterpreterSelectQuery.cpp

@@ -458,20 +458,12 @@ InterpreterSelectQuery::InterpreterSelectQuery(
         }
     }
 
-    /// Check support for JOINs for parallel replicas
-    if (joined_tables.tablesCount() > 1 && (!settings.parallel_replicas_custom_key.value.empty() || settings.allow_experimental_parallel_reading_from_replicas > 0))
+    /// Check support for JOIN for parallel replicas with custom key
+    if (joined_tables.tablesCount() > 1 && !settings.parallel_replicas_custom_key.value.empty())
     {
-        if (settings.allow_experimental_parallel_reading_from_replicas == 1)
-        {
-            LOG_WARNING(log, "JOINs are not supported with parallel replicas. Query will be executed without using them.");
-            context->setSetting("allow_experimental_parallel_reading_from_replicas", Field(0));
+        LOG_WARNING(log, "JOINs are not supported with parallel_replicas_custom_key. Query will be executed without using them.");
         context->setSetting("parallel_replicas_custom_key", String{""});
     }
-        else if (settings.allow_experimental_parallel_reading_from_replicas == 2)
-        {
-            throw Exception(ErrorCodes::SUPPORT_IS_DISABLED, "JOINs are not supported with parallel replicas");
-        }
-    }
 
     /// Check support for FINAL for parallel replicas
     bool is_query_with_final = isQueryWithFinal(query_info);
@@ -489,6 +481,21 @@ InterpreterSelectQuery::InterpreterSelectQuery(
         }
     }
 
+    /// Check support for parallel replicas for non-replicated storage (plain MergeTree)
+    bool is_plain_merge_tree = storage && storage->isMergeTree() && !storage->supportsReplication();
+    if (is_plain_merge_tree && settings.allow_experimental_parallel_reading_from_replicas > 0 && !settings.parallel_replicas_for_non_replicated_merge_tree)
+    {
+        if (settings.allow_experimental_parallel_reading_from_replicas == 1)
+        {
+            LOG_WARNING(log, "To use parallel replicas with plain MergeTree tables please enable setting `parallel_replicas_for_non_replicated_merge_tree`. For now query will be executed without using them.");
+            context->setSetting("allow_experimental_parallel_reading_from_replicas", Field(0));
+        }
+        else if (settings.allow_experimental_parallel_reading_from_replicas == 2)
+        {
+            throw Exception(ErrorCodes::SUPPORT_IS_DISABLED, "To use parallel replicas with plain MergeTree tables please enable setting `parallel_replicas_for_non_replicated_merge_tree`");
+        }
+    }
+
     /// Rewrite JOINs
     if (!has_input && joined_tables.tablesCount() > 1)
     {

src/Interpreters/interpretSubquery.cpp

@@ -112,8 +112,6 @@ std::shared_ptr<InterpreterSelectWithUnionQuery> interpretSubquery(
         subquery_options.removeDuplicates();
     }
 
-    /// We don't want to execute reading for subqueries in parallel
-    subquery_context->setSetting("allow_experimental_parallel_reading_from_replicas", Field(0));
     return std::make_shared<InterpreterSelectWithUnionQuery>(query, subquery_context, subquery_options, required_source_columns);
 }
 

src/Interpreters/threadPoolCallbackRunner.h

@@ -11,13 +11,13 @@ namespace DB
 
 /// High-order function to run callbacks (functions with 'void()' signature) somewhere asynchronously.
 template <typename Result, typename Callback = std::function<Result()>>
-using ThreadPoolCallbackRunner = std::function<std::future<Result>(Callback &&, int64_t priority)>;
+using ThreadPoolCallbackRunner = std::function<std::future<Result>(Callback &&, Priority)>;
 
 /// Creates CallbackRunner that runs every callback with 'pool->scheduleOrThrow()'.
 template <typename Result, typename Callback = std::function<Result()>>
 ThreadPoolCallbackRunner<Result, Callback> threadPoolCallbackRunner(ThreadPool & pool, const std::string & thread_name)
 {
-    return [my_pool = &pool, thread_group = CurrentThread::getGroup(), thread_name](Callback && callback, int64_t priority) mutable -> std::future<Result>
+    return [my_pool = &pool, thread_group = CurrentThread::getGroup(), thread_name](Callback && callback, Priority priority) mutable -> std::future<Result>
     {
         auto task = std::make_shared<std::packaged_task<Result()>>([thread_group, thread_name, my_callback = std::move(callback)]() mutable -> Result
         {
@@ -44,15 +44,14 @@ ThreadPoolCallbackRunner<Result, Callback> threadPoolCallbackRunner(ThreadPool &
 
         auto future = task->get_future();
 
-        /// ThreadPool is using "bigger is higher priority" instead of "smaller is more priority".
-        my_pool->scheduleOrThrow([my_task = std::move(task)]{ (*my_task)(); }, -priority);
+        my_pool->scheduleOrThrow([my_task = std::move(task)]{ (*my_task)(); }, priority);
 
         return future;
     };
 }
 
 template <typename Result, typename T>
-std::future<Result> scheduleFromThreadPool(T && task, ThreadPool & pool, const std::string & thread_name, int64_t priority = 0)
+std::future<Result> scheduleFromThreadPool(T && task, ThreadPool & pool, const std::string & thread_name, Priority priority = {})
 {
     auto schedule = threadPoolCallbackRunner<Result, T>(pool, thread_name);
     return schedule(std::move(task), priority);

src/Parsers/ASTColumnDeclaration.h

@@ -16,7 +16,7 @@ public:
     std::optional<bool> null_modifier;
     String default_specifier;
     ASTPtr default_expression;
-    bool ephemeral_default;
+    bool ephemeral_default = false;
     ASTPtr comment;
     ASTPtr codec;
     ASTPtr ttl;

src/Parsers/ASTDictionaryAttributeDeclaration.h

@@ -19,13 +19,13 @@ public:
     /// Attribute expression
     ASTPtr expression;
     /// Is attribute mirrored to the parent identifier
-    bool hierarchical;
+    bool hierarchical = false;
     /// Is hierarchical attribute bidirectional
-    bool bidirectional;
+    bool bidirectional = false;
     /// Flag that shows whether the id->attribute image is injective
-    bool injective;
+    bool injective = false;
     /// MongoDB object ID
-    bool is_object_id;
+    bool is_object_id = false;
 
     String getID(char delim) const override { return "DictionaryAttributeDeclaration" + (delim + name); }
 

src/Parsers/ASTOrderByElement.h

@@ -11,14 +11,14 @@ namespace DB
 class ASTOrderByElement : public IAST
 {
 public:
-    int direction; /// 1 for ASC, -1 for DESC
-    int nulls_direction; /// Same as direction for NULLS LAST, opposite for NULLS FIRST.
-    bool nulls_direction_was_explicitly_specified;
+    int direction = 0; /// 1 for ASC, -1 for DESC
+    int nulls_direction = 0; /// Same as direction for NULLS LAST, opposite for NULLS FIRST.
+    bool nulls_direction_was_explicitly_specified = false;
 
     /** Collation for locale-specific string comparison. If empty, then sorting done by bytes. */
     ASTPtr collation;
 
-    bool with_fill;
+    bool with_fill = false;
     ASTPtr fill_from;
     ASTPtr fill_to;
     ASTPtr fill_step;

src/Parsers/ASTQueryWithOutput.cpp

@@ -35,6 +35,13 @@ void ASTQueryWithOutput::formatImpl(const FormatSettings & s, FormatState & stat
     {
         s.ostr << (s.hilite ? hilite_keyword : "") << s.nl_or_ws << indent_str << "INTO OUTFILE " << (s.hilite ? hilite_none : "");
         out_file->formatImpl(s, state, frame);
+
+        s.ostr << (s.hilite ? hilite_keyword : "");
+        if (is_outfile_append)
+            s.ostr << " APPEND";
+        if (is_into_outfile_with_stdout)
+            s.ostr << " AND STDOUT";
+        s.ostr << (s.hilite ? hilite_none : "");
     }
 
     if (format)

src/Parsers/ASTQueryWithOutput.h

@@ -15,8 +15,8 @@ class ASTQueryWithOutput : public IAST
 {
 public:
     ASTPtr out_file;
-    bool is_into_outfile_with_stdout;
-    bool is_outfile_append;
+    bool is_into_outfile_with_stdout = false;
+    bool is_outfile_append = false;
     ASTPtr format;
     ASTPtr settings_ast;
     ASTPtr compression;

src/Parsers/ASTWatchQuery.h

@@ -23,7 +23,7 @@ class ASTWatchQuery : public ASTQueryWithTableAndOutput
 
 public:
     ASTPtr limit_length;
-    bool is_watch_events;
+    bool is_watch_events = false;
 
     ASTWatchQuery() = default;
     String getID(char) const override { return "WatchQuery_" + getDatabase() + "_" + getTable(); }

src/Storages/HDFS/AsynchronousReadBufferFromHDFS.cpp

@@ -64,19 +64,19 @@ bool AsynchronousReadBufferFromHDFS::hasPendingDataToRead()
     return true;
 }
 
-std::future<IAsynchronousReader::Result> AsynchronousReadBufferFromHDFS::asyncReadInto(char * data, size_t size, int64_t priority)
+std::future<IAsynchronousReader::Result> AsynchronousReadBufferFromHDFS::asyncReadInto(char * data, size_t size, Priority priority)
 {
     IAsynchronousReader::Request request;
     request.descriptor = std::make_shared<RemoteFSFileDescriptor>(*impl, nullptr);
     request.buf = data;
     request.size = size;
     request.offset = file_offset_of_buffer_end;
-    request.priority = base_priority + priority;
+    request.priority = Priority{base_priority.value + priority.value};
     request.ignore = 0;
     return reader.submit(request);
 }
 
-void AsynchronousReadBufferFromHDFS::prefetch(int64_t priority)
+void AsynchronousReadBufferFromHDFS::prefetch(Priority priority)
 {
     interval_watch.restart();
 

src/Storages/HDFS/AsynchronousReadBufferFromHDFS.h

@@ -33,7 +33,7 @@ public:
 
     off_t seek(off_t offset_, int whence) override;
 
-    void prefetch(int64_t priority) override;
+    void prefetch(Priority priority) override;
 
     size_t getFileSize() override;
 
@@ -50,10 +50,10 @@ private:
 
     bool hasPendingDataToRead();
 
-    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, int64_t priority);
+    std::future<IAsynchronousReader::Result> asyncReadInto(char * data, size_t size, Priority priority);
 
     IAsynchronousReader & reader;
-    int64_t base_priority;
+    Priority base_priority;
     std::shared_ptr<ReadBufferFromHDFS> impl;
     std::future<IAsynchronousReader::Result> prefetch_future;
     Memory<> prefetch_buffer;

src/Storages/MergeTree/IMergeTreeReader.h

@@ -61,7 +61,7 @@ public:
 
     MergeTreeDataPartInfoForReaderPtr data_part_info_for_read;
 
-    virtual void prefetchBeginOfRange(int64_t /* priority */) {}
+    virtual void prefetchBeginOfRange(Priority) {}
 
 protected:
     /// Returns actual column name in part, which can differ from table metadata.

src/Storages/MergeTree/MergeTreeBlockReadUtils.cpp

@@ -142,7 +142,7 @@ MergeTreeReadTask::MergeTreeReadTask(
     const NameSet & column_name_set_,
     const MergeTreeReadTaskColumns & task_columns_,
     MergeTreeBlockSizePredictorPtr size_predictor_,
-    int64_t priority_,
+    Priority priority_,
     std::future<MergeTreeReaderPtr> reader_,
     std::vector<std::future<MergeTreeReaderPtr>> && pre_reader_for_step_)
     : data_part{data_part_}

src/Storages/MergeTree/MergeTreeBlockReadUtils.h

@@ -71,11 +71,7 @@ struct MergeTreeReadTask
     std::future<MergeTreeReaderPtr> reader;
     std::vector<std::future<MergeTreeReaderPtr>> pre_reader_for_step;
 
-    int64_t priority = 0; /// Priority of the task. Bigger value, bigger priority.
-    bool operator <(const MergeTreeReadTask & rhs) const
-    {
-        return priority < rhs.priority;
-    }
+    Priority priority;
 
     bool isFinished() const { return mark_ranges.empty() && range_reader.isCurrentRangeFinished(); }
 
@@ -86,7 +82,7 @@ struct MergeTreeReadTask
         const NameSet & column_name_set_,
         const MergeTreeReadTaskColumns & task_columns_,
         MergeTreeBlockSizePredictorPtr size_predictor_,
-        int64_t priority_ = 0,
+        Priority priority_ = {},
         std::future<MergeTreeReaderPtr> reader_ = {},
         std::vector<std::future<MergeTreeReaderPtr>> && pre_reader_for_step_ = {});
 

src/Storages/MergeTree/MergeTreeData.cpp

@@ -1967,7 +1967,7 @@ try
                 res.part->remove();
             else
                 preparePartForRemoval(res.part);
-        }, 0));
+        }, Priority{}));
     }
 
     /// Wait for every scheduled task

src/Storages/MergeTree/MergeTreePrefetchedReadPool.cpp

@@ -90,7 +90,7 @@ std::future<MergeTreeReaderPtr> MergeTreePrefetchedReadPool::createPrefetchedRea
     const IMergeTreeDataPart & data_part,
     const NamesAndTypesList & columns,
     const MarkRanges & required_ranges,
-    int64_t priority) const
+    Priority priority) const
 {
     auto reader = data_part.getReader(
         columns, storage_snapshot->metadata, required_ranges,
@@ -142,7 +142,7 @@ bool MergeTreePrefetchedReadPool::TaskHolder::operator <(const TaskHolder & othe
 {
     chassert(task->priority >= 0);
     chassert(other.task->priority >= 0);
-    return -task->priority < -other.task->priority; /// Less is better.
+    return task->priority > other.task->priority; /// Less is better.
     /// With default std::priority_queue, top() returns largest element.
     /// So closest to 0 will be on top with this comparator.
 }
@@ -153,7 +153,7 @@ void MergeTreePrefetchedReadPool::startPrefetches() const
         return;
 
     [[maybe_unused]] TaskHolder prev(nullptr, 0);
-    [[maybe_unused]] const int64_t highest_priority = reader_settings.read_settings.priority + 1;
+    [[maybe_unused]] const Priority highest_priority{reader_settings.read_settings.priority.value + 1};
     assert(prefetch_queue.top().task->priority == highest_priority);
     while (!prefetch_queue.empty())
     {
@@ -495,11 +495,11 @@ MergeTreePrefetchedReadPool::ThreadsTasks MergeTreePrefetchedReadPool::createThr
         auto need_marks = min_marks_per_thread;
 
         /// Priority is given according to the prefetch number for each thread,
-        /// e.g. the first task of each thread has the same priority and is bigger
-        /// than second task of each thread, and so on.
+        /// e.g. the first task of each thread has the same priority and is greater
+        /// than the second task of each thread, and so on.
         /// Add 1 to query read priority because higher priority should be given to
         /// reads from pool which are from reader.
-        int64_t priority = reader_settings.read_settings.priority + 1;
+        Priority priority{reader_settings.read_settings.priority.value + 1};
 
         while (need_marks > 0 && part_idx < parts_infos.size())
         {
@@ -597,7 +597,7 @@ MergeTreePrefetchedReadPool::ThreadsTasks MergeTreePrefetchedReadPool::createThr
             {
                 prefetch_queue.emplace(TaskHolder(read_task.get(), i));
             }
-            ++priority;
+            ++priority.value;
 
             result_threads_tasks[i].push_back(std::move(read_task));
         }

src/Storages/MergeTree/MergeTreePrefetchedReadPool.h

@@ -53,12 +53,11 @@ private:
     using ThreadTasks = std::deque<MergeTreeReadTaskPtr>;
     using ThreadsTasks = std::map<size_t, ThreadTasks>;
 
-    /// smaller `priority` means more priority
     std::future<MergeTreeReaderPtr> createPrefetchedReader(
         const IMergeTreeDataPart & data_part,
         const NamesAndTypesList & columns,
         const MarkRanges & required_ranges,
-        int64_t priority) const;
+        Priority priority) const;
 
     void createPrefetchedReaderForTask(MergeTreeReadTask & task) const;
 

src/Storages/MergeTree/MergeTreeReaderCompact.cpp

@@ -314,7 +314,7 @@ void MergeTreeReaderCompact::readData(
         last_read_granule.emplace(from_mark, column_position);
 }
 
-void MergeTreeReaderCompact::prefetchBeginOfRange(int64_t priority)
+void MergeTreeReaderCompact::prefetchBeginOfRange(Priority priority)
 {
     if (!initialized)
     {

src/Storages/MergeTree/MergeTreeReaderCompact.h

@@ -38,7 +38,7 @@ public:
 
     bool canReadIncompleteGranules() const override { return false; }
 
-    void prefetchBeginOfRange(int64_t priority) override;
+    void prefetchBeginOfRange(Priority priority) override;
 
 private:
     bool isContinuousReading(size_t mark, size_t column_position);

src/Storages/MergeTree/MergeTreeReaderWide.cpp

@@ -58,7 +58,7 @@ MergeTreeReaderWide::MergeTreeReaderWide(
     }
 }
 
-void MergeTreeReaderWide::prefetchBeginOfRange(int64_t priority)
+void MergeTreeReaderWide::prefetchBeginOfRange(Priority priority)
 {
     prefetched_streams.clear();
 
@@ -90,7 +90,7 @@ void MergeTreeReaderWide::prefetchBeginOfRange(int64_t priority)
 }
 
 void MergeTreeReaderWide::prefetchForAllColumns(
-    int64_t priority, size_t num_columns, size_t from_mark, size_t current_task_last_mark, bool continue_reading)
+    Priority priority, size_t num_columns, size_t from_mark, size_t current_task_last_mark, bool continue_reading)
 {
     bool do_prefetch = data_part_info_for_read->getDataPartStorage()->isStoredOnRemoteDisk()
         ? settings.read_settings.remote_fs_prefetch
@@ -137,7 +137,7 @@ size_t MergeTreeReaderWide::readRows(
         if (num_columns == 0)
             return max_rows_to_read;
 
-        prefetchForAllColumns(/* priority */0, num_columns, from_mark, current_task_last_mark, continue_reading);
+        prefetchForAllColumns(Priority{}, num_columns, from_mark, current_task_last_mark, continue_reading);
 
         for (size_t pos = 0; pos < num_columns; ++pos)
         {
@@ -305,7 +305,7 @@ void MergeTreeReaderWide::deserializePrefix(
 }
 
 void MergeTreeReaderWide::prefetchForColumn(
-    int64_t priority,
+    Priority priority,
     const NameAndTypePair & name_and_type,
     const SerializationPtr & serialization,
     size_t from_mark,

src/Storages/MergeTree/MergeTreeReaderWide.h

@@ -33,14 +33,14 @@ public:
 
     bool canReadIncompleteGranules() const override { return true; }
 
-    void prefetchBeginOfRange(int64_t priority) override;
+    void prefetchBeginOfRange(Priority priority) override;
 
     using FileStreams = std::map<std::string, std::unique_ptr<MergeTreeReaderStream>>;
 
 private:
     FileStreams streams;
 
-    void prefetchForAllColumns(int64_t priority, size_t num_columns, size_t from_mark, size_t current_task_last_mark, bool continue_reading);
+    void prefetchForAllColumns(Priority priority, size_t num_columns, size_t from_mark, size_t current_task_last_mark, bool continue_reading);
 
     void addStreams(
         const NameAndTypePair & name_and_type,
@@ -55,7 +55,7 @@ private:
 
     /// Make next readData more simple by calling 'prefetch' of all related ReadBuffers (column streams).
     void prefetchForColumn(
-        int64_t priority,
+        Priority priority,
         const NameAndTypePair & name_and_type,
         const SerializationPtr & serialization,
         size_t from_mark,

src/Storages/MergeTree/MergeTreeSource.cpp

@@ -84,7 +84,7 @@ struct MergeTreeSource::AsyncReadingState
     {
         try
         {
-            callback_runner(std::move(job), 0);
+            callback_runner(std::move(job), Priority{});
         }
         catch (...)
         {

src/Storages/StorageS3.cpp

@@ -356,7 +356,7 @@ private:
                 request.SetContinuationToken(outcome.GetResult().GetNextContinuationToken());
 
             return outcome;
-        }, 0);
+        }, Priority{});
     }
 
     std::mutex mutex;
@@ -619,7 +619,7 @@ StorageS3Source::ReaderHolder StorageS3Source::createReader()
 
 std::future<StorageS3Source::ReaderHolder> StorageS3Source::createReaderAsync()
 {
-    return create_reader_scheduler([this] { return createReader(); }, 0);
+    return create_reader_scheduler([this] { return createReader(); }, Priority{});
 }
 
 StorageS3Source::ReadBufferOrFactory StorageS3Source::createS3ReadBuffer(const String & key, size_t object_size)

tests/queries/0_stateless/02415_all_new_functions_must_be_documented.reference

@@ -655,6 +655,7 @@ sleep
 sleepEachRow
 snowflakeToDateTime
 snowflakeToDateTime64
+space
 splitByChar
 splitByNonAlpha
 splitByRegexp

tests/queries/0_stateless/02535_max_parallel_replicas_custom_key.sh

@@ -41,6 +41,6 @@ run_count_with_custom_key "y"
 run_count_with_custom_key "cityHash64(y)"
 run_count_with_custom_key "cityHash64(y) + 1"
 
-$CLICKHOUSE_CLIENT --query="SELECT count() FROM cluster(test_cluster_one_shard_three_replicas_localhost, currentDatabase(), 02535_custom_key) as t1 JOIN 02535_custom_key USING y" --parallel_replicas_custom_key="y" --send_logs_level="trace" 2>&1 | grep -Fac "JOINs are not supported with parallel replicas"
+$CLICKHOUSE_CLIENT --query="SELECT count() FROM cluster(test_cluster_one_shard_three_replicas_localhost, currentDatabase(), 02535_custom_key) as t1 JOIN 02535_custom_key USING y" --parallel_replicas_custom_key="y" --send_logs_level="trace" 2>&1 | grep -Fac "JOINs are not supported with"
 
 $CLICKHOUSE_CLIENT --query="DROP TABLE 02535_custom_key"

tests/queries/0_stateless/02708_parallel_replicas_not_found_column.sql

@@ -1,3 +1,4 @@
 CREATE TABLE IF NOT EXISTS t_02708(x DateTime) ENGINE = MergeTree ORDER BY tuple();
+SET send_logs_level='error';
 SELECT count() FROM t_02708 SETTINGS allow_experimental_parallel_reading_from_replicas=1;
 DROP TABLE t_02708;

tests/queries/0_stateless/02731_parallel_replicas_join_subquery.reference

@@ -0,0 +1,44 @@
+=============== INNER QUERY (NO PARALLEL) ===============
+0	PJFiUe#J2O	_s\'	14427935816175499794
+1	>T%O	,z<	17537932797009027240
+12	D[6,P	#}Lmb[ ZzU	6394957109822140795
+18		$_N-	24422838680427462
+2	bX?}ix [	Ny]2 G	16242612901291874718
+20	VE]	Y	15120036904703536841
+22	Ti~3)N)<	A!( 3	18361093572663329113
+23	Sx>b:^UG	XpedE)Q:	7433019734386307503
+29	2j&S)ba?XG	QuQj	17163829389637435056
+3	UlI+1		14144472852965836438
+=============== INNER QUERY (PARALLEL) ===============
+0	PJFiUe#J2O	_s\'	14427935816175499794
+1	>T%O	,z<	17537932797009027240
+12	D[6,P	#}Lmb[ ZzU	6394957109822140795
+18		$_N-	24422838680427462
+2	bX?}ix [	Ny]2 G	16242612901291874718
+20	VE]	Y	15120036904703536841
+22	Ti~3)N)<	A!( 3	18361093572663329113
+23	Sx>b:^UG	XpedE)Q:	7433019734386307503
+29	2j&S)ba?XG	QuQj	17163829389637435056
+3	UlI+1		14144472852965836438
+=============== QUERIES EXECUTED BY PARALLEL INNER QUERY ALONE ===============
+0	3	SELECT `key`, `value1`, `value2`, toUInt64(min(`time`)) AS `start_ts` FROM `default`.`join_inner_table` PREWHERE (`id` = \'833c9e22-c245-4eb5-8745-117a9a1f26b1\') AND (`number` > toUInt64(\'1610517366120\')) GROUP BY `key`, `value1`, `value2` ORDER BY `key` ASC, `value1` ASC, `value2` ASC LIMIT 10
+1	1	-- Parallel inner query alone\nSELECT\n    key,\n    value1,\n    value2,\n    toUInt64(min(time)) AS start_ts\nFROM join_inner_table\nPREWHERE (id = \'833c9e22-c245-4eb5-8745-117a9a1f26b1\') AND (number > toUInt64(\'1610517366120\'))\nGROUP BY key, value1, value2\nORDER BY key, value1, value2\nLIMIT 10\nSETTINGS allow_experimental_parallel_reading_from_replicas = 1;
+=============== OUTER QUERY (NO PARALLEL) ===============
+>T%O	,z<	10
+NQTpY#	W\\Xx4	10
+PJFiUe#J2O	_s\'	10
+U	c	10
+UlI+1		10
+bX?}ix [	Ny]2 G	10
+t<iT	X48q:Z]t0	10
+=============== OUTER QUERY (PARALLEL) ===============
+>T%O	,z<	10
+NQTpY#	W\\Xx4	10
+PJFiUe#J2O	_s\'	10
+U	c	10
+UlI+1		10
+bX?}ix [	Ny]2 G	10
+t<iT	X48q:Z]t0	10
+0	3	SELECT `key`, `value1`, `value2`, toUInt64(min(`time`)) AS `start_ts` FROM `default`.`join_inner_table` PREWHERE (`id` = \'833c9e22-c245-4eb5-8745-117a9a1f26b1\') AND (`number` > toUInt64(\'1610517366120\')) GROUP BY `key`, `value1`, `value2`
+0	3	SELECT `value1`, `value2`, count() AS `count` FROM `default`.`join_outer_table` ALL INNER JOIN `_data_11888098645495698704_17868075224240210014` USING (`key`) GROUP BY `key`, `value1`, `value2`
+1	1	-- Parallel full query\nSELECT\n    value1,\n    value2,\n    avg(count) AS avg\nFROM\n    (\n        SELECT\n            key,\n            value1,\n            value2,\n            count() AS count\n        FROM join_outer_table\n        INNER JOIN\n        (\n            SELECT\n                key,\n                value1,\n                value2,\n                toUInt64(min(time)) AS start_ts\n            FROM join_inner_table\n            PREWHERE (id = \'833c9e22-c245-4eb5-8745-117a9a1f26b1\') AND (number > toUInt64(\'1610517366120\'))\n            GROUP BY key, value1, value2\n        ) USING (key)\n        GROUP BY key, value1, value2\n        )\nGROUP BY value1, value2\nORDER BY value1, value2\nSETTINGS allow_experimental_parallel_reading_from_replicas = 1;

tests/queries/0_stateless/02731_parallel_replicas_join_subquery.sql

@@ -0,0 +1,182 @@
+-- Tags: zookeeper
+
+CREATE TABLE join_inner_table
+(
+    id UUID,
+    key String,
+    number Int64,
+    value1 String,
+    value2 String,
+    time Int64
+)
+ENGINE=ReplicatedMergeTree('/clickhouse/tables/{database}/join_inner_table', 'r1')
+ORDER BY (id, number, key);
+
+INSERT INTO join_inner_table
+SELECT
+    '833c9e22-c245-4eb5-8745-117a9a1f26b1'::UUID as id,
+    rowNumberInAllBlocks()::String as key,
+    * FROM generateRandom('number Int64, value1 String, value2 String, time Int64', 1, 10, 2)
+LIMIT 100;
+
+SET allow_experimental_analyzer = 0;
+SET max_parallel_replicas = 3;
+SET prefer_localhost_replica = 1;
+SET cluster_for_parallel_replicas = 'test_cluster_one_shard_three_replicas_localhost';
+SET use_hedged_requests = 0;
+SET joined_subquery_requires_alias = 0;
+
+SELECT '=============== INNER QUERY (NO PARALLEL) ===============';
+
+SELECT
+    key,
+    value1,
+    value2,
+    toUInt64(min(time)) AS start_ts
+FROM join_inner_table
+    PREWHERE (id = '833c9e22-c245-4eb5-8745-117a9a1f26b1') AND (number > toUInt64('1610517366120'))
+GROUP BY key, value1, value2
+ORDER BY key, value1, value2
+LIMIT 10;
+
+SELECT '=============== INNER QUERY (PARALLEL) ===============';
+
+-- Parallel inner query alone
+SELECT
+    key,
+    value1,
+    value2,
+    toUInt64(min(time)) AS start_ts
+FROM join_inner_table
+PREWHERE (id = '833c9e22-c245-4eb5-8745-117a9a1f26b1') AND (number > toUInt64('1610517366120'))
+GROUP BY key, value1, value2
+ORDER BY key, value1, value2
+LIMIT 10
+SETTINGS allow_experimental_parallel_reading_from_replicas = 1;
+
+SELECT '=============== QUERIES EXECUTED BY PARALLEL INNER QUERY ALONE ===============';
+
+SYSTEM FLUSH LOGS;
+-- There should be 4 queries. The main query as received by the initiator and the 3 equal queries sent to each replica
+SELECT is_initial_query, count() as c, query,
+FROM system.query_log
+WHERE
+      event_date >= yesterday()
+  AND type = 'QueryFinish'
+  AND initial_query_id =
+      (
+          SELECT query_id
+          FROM system.query_log
+          WHERE
+                current_database = currentDatabase()
+            AND event_date >= yesterday()
+            AND type = 'QueryFinish'
+            AND query LIKE '-- Parallel inner query alone%'
+      )
+GROUP BY is_initial_query, query
+ORDER BY is_initial_query, c, query;
+
+---- Query with JOIN
+
+CREATE TABLE join_outer_table
+(
+    id UUID,
+    key String,
+    otherValue1 String,
+    otherValue2 String,
+    time Int64
+)
+ENGINE = ReplicatedMergeTree('/clickhouse/tables/{database}/join_outer_table', 'r1')
+ORDER BY (id, time, key);
+
+INSERT INTO join_outer_table
+SELECT
+    '833c9e22-c245-4eb5-8745-117a9a1f26b1'::UUID as id,
+        (rowNumberInAllBlocks() % 10)::String as key,
+        * FROM generateRandom('otherValue1 String, otherValue2 String, time Int64', 1, 10, 2)
+LIMIT 100;
+
+
+SELECT '=============== OUTER QUERY (NO PARALLEL) ===============';
+
+SELECT
+    value1,
+    value2,
+    avg(count) AS avg
+FROM
+(
+    SELECT
+        key,
+        value1,
+        value2,
+        count() AS count
+    FROM join_outer_table
+    INNER JOIN
+    (
+        SELECT
+            key,
+            value1,
+            value2,
+            toUInt64(min(time)) AS start_ts
+        FROM join_inner_table
+        PREWHERE (id = '833c9e22-c245-4eb5-8745-117a9a1f26b1') AND (number > toUInt64('1610517366120'))
+        GROUP BY key, value1, value2
+    ) USING (key)
+    GROUP BY key, value1, value2
+)
+GROUP BY value1, value2
+ORDER BY value1, value2;
+
+SELECT '=============== OUTER QUERY (PARALLEL) ===============';
+
+-- Parallel full query
+SELECT
+    value1,
+    value2,
+    avg(count) AS avg
+FROM
+    (
+        SELECT
+            key,
+            value1,
+            value2,
+            count() AS count
+        FROM join_outer_table
+        INNER JOIN
+        (
+            SELECT
+                key,
+                value1,
+                value2,
+                toUInt64(min(time)) AS start_ts
+            FROM join_inner_table
+            PREWHERE (id = '833c9e22-c245-4eb5-8745-117a9a1f26b1') AND (number > toUInt64('1610517366120'))
+            GROUP BY key, value1, value2
+        ) USING (key)
+        GROUP BY key, value1, value2
+        )
+GROUP BY value1, value2
+ORDER BY value1, value2
+SETTINGS allow_experimental_parallel_reading_from_replicas = 1;
+
+SYSTEM FLUSH LOGS;
+
+-- There should be 7 queries. The main query as received by the initiator, the 3 equal queries to execute the subquery
+-- in the inner join and the 3 queries executing the whole query (but replacing the subquery with a temp table)
+SELECT is_initial_query, count() as c, query,
+FROM system.query_log
+WHERE
+      event_date >= yesterday()
+  AND type = 'QueryFinish'
+  AND initial_query_id =
+      (
+          SELECT query_id
+          FROM system.query_log
+          WHERE
+                current_database = currentDatabase()
+            AND event_date >= yesterday()
+            AND type = 'QueryFinish'
+            AND query LIKE '-- Parallel full query%'
+      )
+GROUP BY is_initial_query, query
+ORDER BY is_initial_query, c, query;

tests/queries/0_stateless/02751_parallel_replicas_bug_chunkinfo_not_set.sql

@@ -0,0 +1,43 @@
+CREATE TABLE join_inner_table__fuzz_1
+(
+    `id` UUID,
+    `key` Nullable(Date),
+    `number` Int64,
+    `value1` LowCardinality(String),
+    `value2` LowCardinality(String),
+    `time` Int128
+)
+ENGINE = MergeTree
+ORDER BY (id, number, key)
+SETTINGS allow_nullable_key = 1;
+
+INSERT INTO join_inner_table__fuzz_1 SELECT
+    CAST('833c9e22-c245-4eb5-8745-117a9a1f26b1', 'UUID') AS id,
+    CAST(rowNumberInAllBlocks(), 'String') AS key,
+    *
+FROM generateRandom('number Int64, value1 String, value2 String, time Int64', 1, 10, 2)
+LIMIT 100;
+
+SET max_parallel_replicas = 3,  prefer_localhost_replica = 1, use_hedged_requests = 0, cluster_for_parallel_replicas = 'test_cluster_one_shard_three_replicas_localhost', allow_experimental_parallel_reading_from_replicas = 1;
+
+-- SELECT query will write a Warning to the logs
+SET send_logs_level='error';
+
+SELECT
+    key,
+    value1,
+    value2,
+    toUInt64(min(time)) AS start_ts
+FROM join_inner_table__fuzz_1
+PREWHERE (id = '833c9e22-c245-4eb5-8745-117a9a1f26b1') AND (number > toUInt64('1610517366120'))
+GROUP BY
+    key,
+    value1,
+    value2
+    WITH ROLLUP
+ORDER BY
+    key ASC,
+    value1 ASC,
+    value2 ASC NULLS LAST
+LIMIT 10
+FORMAT Null;

tests/queries/0_stateless/02752_space_function.reference

@@ -0,0 +1,86 @@
+const, uint
+   	3
+   	3
+   	3
+   	3
+const, int
+   	3
+   	3
+   	3
+   	3
+const, int, negative
+	0
+	0
+	0
+	0
+negative tests
+null
+\N
+const, uint, multiple
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+const int, multiple
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+                              
+non-const, uint
+   	3
+  	2
+ 	1
+	0
+            	12
+          	10
+    	4
+     	5
+    	4
+                     	21
+         	9
+       	7
+                                                        	56
+                    	20
+     	5
+       	7
+non-const, int
+   	3
+  	2
+ 	1
+	0
+            	12
+          	10
+    	4
+     	5
+	0
+	0
+	0
+	0
+                                                        	56
+                    	20
+     	5
+       	7

tests/queries/0_stateless/02752_space_function.sql

@@ -0,0 +1,64 @@
+SELECT 'const, uint';
+SELECT space(3::UInt8), length(space(3::UInt8));
+SELECT space(3::UInt16), length(space(3::UInt16));
+SELECT space(3::UInt32), length(space(3::UInt32));
+SELECT space(3::UInt64), length(space(3::UInt64));
+SELECT 'const, int';
+SELECT space(3::Int8), length(space(3::Int8));
+SELECT space(3::Int16), length(space(3::Int16));
+SELECT space(3::Int32), length(space(3::Int32));
+SELECT space(3::Int64), length(space(3::Int64));
+
+SELECT 'const, int, negative';
+SELECT space(-3::Int8), length(space(-3::Int8));
+SELECT space(-3::Int16), length(space(-3::Int16));
+SELECT space(-3::Int32), length(space(-3::Int32));
+SELECT space(-3::Int64), length(space(-3::Int64));
+
+SELECT 'negative tests';
+SELECT space('abc'); -- { serverError ILLEGAL_TYPE_OF_ARGUMENT }
+SELECT space(['abc']); -- { serverError ILLEGAL_TYPE_OF_ARGUMENT }
+SELECT space(('abc')); -- { serverError ILLEGAL_TYPE_OF_ARGUMENT }
+SELECT space(30303030303030303030303030303030::UInt64); -- { serverError TOO_LARGE_STRING_SIZE }
+
+SELECT 'null';
+SELECT space(NULL);
+
+DROP TABLE IF EXISTS defaults;
+CREATE TABLE defaults
+(
+    u8 UInt8,
+    u16 UInt16,
+    u32 UInt32,
+    u64 UInt64,
+    i8 Int8,
+    i16 Int16,
+    i32 Int32,
+    i64 Int64
+) ENGINE = Memory();
+
+INSERT INTO defaults values (3, 12, 4, 56, 3, 12, -4, 56) (2, 10, 21, 20, 2, 10, -21, 20) (1, 4, 9, 5, 1, 4, -9, 5) (0, 5, 7, 7, 0, 5, -7, 7);
+
+SELECT 'const, uint, multiple';
+SELECT space(30::UInt8) FROM defaults;
+SELECT space(30::UInt16) FROM defaults;
+SELECT space(30::UInt32) FROM defaults;
+SELECT space(30::UInt64) FROM defaults;
+SELECT 'const int, multiple';
+SELECT space(30::Int8) FROM defaults;
+SELECT space(30::Int16) FROM defaults;
+SELECT space(30::Int32) FROM defaults;
+SELECT space(30::Int64) FROM defaults;
+
+SELECT 'non-const, uint';
+SELECT space(u8), length(space(u8)) FROM defaults;
+SELECT space(u16), length(space(u16)) FROM defaults;
+SELECT space(u32), length(space(u32)) from defaults;
+SELECT space(u64), length(space(u64)) FROM defaults;
+SELECT 'non-const, int';
+SELECT space(i8), length(space(i8)) FROM defaults;
+SELECT space(i16), length(space(i16)) FROM defaults;
+SELECT space(i32), length(space(i32)) from defaults;
+SELECT space(i64), length(space(i64)) FROM defaults;
+
+DROP TABLE defaults;

tests/queries/0_stateless/02764_parallel_replicas_plain_merge_tree.sql

@@ -2,7 +2,7 @@ CREATE TABLE IF NOT EXISTS parallel_replicas_plain (x String) ENGINE=MergeTree()
 INSERT INTO parallel_replicas_plain SELECT toString(number) FROM numbers(10);
 
 SET max_parallel_replicas=3, allow_experimental_parallel_reading_from_replicas=1, use_hedged_requests=0, cluster_for_parallel_replicas='parallel_replicas';
-
+SET send_logs_level='error';
 SET parallel_replicas_for_non_replicated_merge_tree = 0;
 
 SELECT x FROM parallel_replicas_plain LIMIT 1 FORMAT Null;

tests/queries/0_stateless/02767_into_outfile_extensions_msan.reference

@@ -0,0 +1,2 @@
+Expression ((Projection + Before ORDER BY))
+  ReadFromStorage (SystemNumbers)

tests/queries/0_stateless/02767_into_outfile_extensions_msan.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+CUR_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CUR_DIR"/../shell_config.sh
+
+out="explain1.$CLICKHOUSE_TEST_UNIQUE_NAME.out"
+# only EXPLAIN triggers the problem under MSan
+$CLICKHOUSE_CLIENT -q "explain select * from numbers(1) into outfile '$out'"
+cat "$out"
+rm -f "$out"

tests/queries/0_stateless/02768_into_outfile_extensions_format.reference

@@ -0,0 +1,20 @@
+SELECT *
+FROM numbers(1)
+INTO OUTFILE '/dev/null'
+;
+
+SELECT *
+FROM numbers(1)
+INTO OUTFILE '/dev/null' AND STDOUT
+;
+
+SELECT *
+FROM numbers(1)
+INTO OUTFILE '/dev/null' APPEND
+;
+
+SELECT *
+FROM numbers(1)
+INTO OUTFILE '/dev/null' APPEND AND STDOUT
+;
+

tests/queries/0_stateless/02768_into_outfile_extensions_format.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+CUR_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CUR_DIR"/../shell_config.sh
+
+echo "
+select * from numbers(1) into outfile '/dev/null';
+select * from numbers(1) into outfile '/dev/null' and stdout;
+select * from numbers(1) into outfile '/dev/null' append;
+select * from numbers(1) into outfile '/dev/null' append and stdout;
+" | clickhouse-format -n