ClickHouse/docs/changelogs/v21.1.1.5646-prestable.md

ClickHouse release v21.1.1.5646-prestable FIXME as compared to v20.12.1.5236-prestable

Backward Incompatible Change

• Prohibit toUnixTimestamp(Date()) (before it just returns UInt16 representation of Date). #17376 (Azat Khuzhin).
• Removed aggregate functions timeSeriesGroupSum, timeSeriesGroupRateSum because a friend of mine said they never worked. This fixes #16869. If you have luck using these functions, write a email to clickhouse-feedback@yandex-team.com. #17423 (Alexey Milovidov).
• The setting input_format_null_as_default is enabled by default. #17525 (Alexey Milovidov).
• Set insert_quorum_parallel to 1 by default. It is significantly more convenient to use than "sequential" quorum inserts. But if you rely to sequential consistency, you should set the setting back to zero. #17567 (Alexey Milovidov).
• Restrict ALTER MODIFY SETTING from changing storage settings that affects data parts (write_final_mark and enable_mixed_granularity_parts). #18306 (Amos Bird).
• Check settings constraints for profile settings from config. Server will fail to start if users.xml contain settings that do not meet corresponding constraints. #18486 (Alexander Tokmakov).
• Remove sumburConsistentHash function. This closes #18120. #18656 (Alexey Milovidov).
• Add DIV and MOD operators. DIV implements integer division. This is needed for MySQL compatibility and for sqllogictest. This closes #18707. It may introduce incompatibilities if you are using DIV or MOD as column names or aliases. In case of incompatibility, write aliases after AS keyword or wrap identifiers in quotes (either double quotes or backquotes). #18760 (Du Chuan).

New Feature

• Use https://github.com/lemire/fast_float to parse floating point numbers. #16787 (Maksim Kita).
• ... #16819 (pronvis).
• Provide a new aggregator combinator : -SimpleState to build SimpleAggregateFunction types via query. It's useful for defining MaterializedView of AggregatingMergeTree engine, and will benefit projections too. #16853 (Amos Bird).
• Added mannWitneyUTest, studentTTest and welchTTest aggregate functions. Refactored RankCorr a bit. #16883 (Nikita Mikhaylov).
• Add a setting optimize_on_insert. When enabled, do the same transformation for INSERTed block of data as if merge was done on this block (e.g. Replacing, Collapsing, Aggregating...). This setting will be enabled as default. This can influence Materialized View and MaterializeMySQL behaviour (see detailed description). This closes #10683. #16954 (Kruglov Pavel).
• add *.zst compression/decompression support.It enables using *.zst in file() function and Content-encoding: zstd in http client.This closes #16791 . #17144 (Abi Palagashvili).
• • IP Dictionary supports IPv4 / IPv6 types directly. #17571 (Vladimir C).
• related: #16176 Usage: set limit = 10; set offset = 20; this two settings will affect SELECT query as if it is added like select * from ($your_original_select_query) tmp limit xxx offset xxx;. #17633 (hexiaoting).
• Add asynchronous metrics on total amount of rows, bytes and parts in MergeTree tables. This fix #11714. #17639 (flynn).
• Introduce DETACH TABLE/VIEW ... PERMANENTLY syntax, so that after restarting the table does not reappear back automatically (only by explicit request). The table can still be attached back using the short syntax ATTACH TABLE. Implements #5555. Fixes #13850. #17642 (filimonov).
• Adds a new table called system.distributed_ddl_queue that displays the queries in the DDL worker queue. #17656 (Bharat Nallan).
• Add function encodeXMLComponent to escape characters to place string into XML text node or attribute. #17659 (nauta).
• Now clickhouse-client supports opening EDITOR to edit commands. Alt-Shift-E. #17665 (Amos Bird).
• Add support for PROXYv1 protocol to wrap native TCP interface. Allow quotas to be keyed by proxy-forwarded IP address (applied for PROXYv1 address and for X-Forwarded-For from HTTP interface). This is useful when you provide access to ClickHouse only via trusted proxy (e.g. CloudFlare) but want to account user resources by their original IP addresses. This fixes #17268. #17707 (Alexey Milovidov).
• Add ability to use custom TLD list in functions firstSignificantSubdomainCustom, cutToFirstSignificantSubdomainCustom. #17748 (Azat Khuzhin).
• Clickhouse-benchmark added query parameter. #17832 (Maksim Kita).
• Extended OPTIMIZE ... DEDUPLICATE syntax to allow explicit (or implicit with asterisk/column transformers) list of columns to check for duplicates on. ... #17846 (Vasily Nemkov).
• Add settings min_compress_block_size and max_compress_block_size to MergeTreeSettings, which have higher priority than the global settings and take effect when they are set. close 13890. #17867 (flynn).
• Implemented ATTACH TABLE name FROM 'path/to/data/' (col1 Type1, ... query. It creates new table with provided structure and attaches table data from provided directory in user_files. #17903 (Alexander Tokmakov).
• Added arrayMin, arrayMax, arrayAvg aggregation functions. #18032 (Maksim Kita).
• Support SHOW SETTINGS statement to show parameters in system.settings. SHOW CHANGED SETTINGS and LIKE/ILIKE clause are also supported. #18056 (Jianmei Zhang).
• Allow create table as select with columns specification. Example CREATE TABLE t1 (x String) ENGINE = Memory AS SELECT 1;. #18060 (Maksim Kita).
• • IP Dictionary supports key fetching. Resolves #18241. #18480 (Vladimir C).
• Implemented REPLACE TABLE and CREATE OR REPLACE TABLE queries. #18521 (Alexander Tokmakov).
• Added function byteSize to estimate of uncompressed byte size of its arguments in memory. E.g. for UInt32 argument it will return constant 4, for String argument - the string length + 9. The function can take multiple arguments. The typical application is byteSize(*). #18579 (Ping Yu).
• Add query_id column to system.part_log for inserted parts. closes #10097. #18644 (flynn).
• Now we have a new storage setting max_partitions_to_read for tables in the MergeTree family. It limits the max number of partitions that can be accessed in one query. A user setting force_max_partition_limit is also added to enforce this constraint. #18712 (Amos Bird).
• Function position now supports position(needle in haystack) synax for SQL compatibility. This closes #18701. ... #18779 (Jianmei Zhang).

Performance Improvement

• Slightly improved performance of float parsing. #16809 (Maksim Kita).
• Improved performance of function repeat. #16937 (satanson).
• Fix performance of reading from Merge tables over huge number of MergeTree tables. Fixes #7748. #16988 (Anton Popov).
• Now the -If combinator is devirtualized, and count is properly vectorized. This is for https://github.com/ClickHouse/ClickHouse/pull/17041. #17043 (Amos Bird).
• Improve performance of AggregatingMergeTree w/ SimpleAggregateFunction(String) in PK. #17109 (Azat Khuzhin).
• Add remerge_sort_lowered_memory_bytes_ratio setting (If memory usage after remerge does not reduced by this ratio, remerge will be disabled). #17539 (Azat Khuzhin).
• Speedup IPv6CIDRToRange implementation. #17569 (Vladimir C).
• Using dragonbox algorithm for float to string conversion instead of ryu. #17831 (Maksim Kita).
• Optimized read for StorageMemory. #18052 (Maksim Kita).
• Don't send empty blocks to shards on synchronous INSERT into Distributed table. This closes #14571. #18775 (Alexey Milovidov).
• Replace PODArray with PODArrayWithStackMemory in AggregateFunctionWindowFunnelData to improvement windowFunnel function performance. #18817 (flynn).
• Add --no-system-table option for clickhouse-local to run without system tables. This avoids initialization of DateLUT that may take noticeable amount of time (tens of milliseconds) at startup. #18899 (Alexey Milovidov).

Improvement

• • New IP Dictionary implementation with lower memory consumption, improved performance for some cases, and fixed bugs. #16804 (Vladimir C).
• Added proper authentication using environment, ~/.aws and AssumeRole for S3 client. #16856 (Vladimir Chebotarev).
• Support HTTP proxy and HTTPS S3 endpoint configuration. #16861 (Pavel Kovalenko).
• When -OrNull combinator combined -If, -Merge, -MergeState, -State combinators, we should put -OrNull in front. #16935 (flynn).
• • Add configuration for multi zookeeper clusters. #17070 (fastio).
• • Add limit for http redirects in request to S3 storage ('s3_max_redirects'). #17220 (ianton-ru).
• Now set indices will work with GLOBAL IN. This fixes #17232 , #5576 . #17253 (Amos Bird).
• Avoid possible stack overflow in bigint conversion. Big integers are experimental. #17269 (flynn).
• Improved minimal Web UI: add history; add sharing support; avoid race condition of different requests; add request in-flight and ready indicators; add favicon; detect Ctrl+Enter if textarea is not in focus. #17293 (Alexey Milovidov).
• Allow to use optimize_move_to_prewhere optimization with compact parts, when sizes of columns are unknown. #17330 (Anton Popov).
• Implement countSubstrings()/countSubstringsCaseInsensitive()/countSubstringsCaseInsensitiveUTF8() (Count the number of substring occurrences). #17347 (Azat Khuzhin).
• Add eof check in receiveHello to prevent getting Attempt to read after eof exception. #17365 (Kruglov Pavel).
• Replaced malloc with new, so that the MemoryTracker takes this memory into account. #17412 (Nikita Mikhaylov).
• Fix parsing of SETTINGS clause of the INSERT ... SELECT ... SETTINGS query. #17414 (Azat Khuzhin).
• Multiple improvements in ./clickhouse install script. #17421 (Alexey Milovidov).
• Simplify Sys/V init script. It was not working on Ubuntu 12.04. #17428 (Alexey Milovidov).
• Now queries coming to the server via MySQL and PostgreSQL protocols have distinctive interface types (which can be seen in the interface column of the tablesystem.query_log): 4 for MySQL, and 5 for PostgreSQL, instead of formerly used 1 which is now used for the native protocol only. #17437 (Vitaly Baranov).
• Allow specifying TTL to remove old entries from system log tables, using the <ttl> attribute in config.xml. #17438 (Du Chuan).
• Add functions countMatches/countMatchesCaseInsensitive. #17459 (Azat Khuzhin).
• Return dynamic columns like MATERIALIZED / ALIAS for wildcard query when switches asterisk_include_materialized_columns and asterisk_include_alias_columns are turned on. #17462 (Ken Chen).
• Export asynchronous metrics of all servers current threads. It's useful to track down issues like https://github.com/ClickHouse-Extras/poco/pull/28. #17463 (Amos Bird).
• Export current max ddl entry executed by DDLWorker. It's useful to check if DDLWorker hangs somewhere. #17464 (Amos Bird).
• Query obfuscator: avoid usage of some SQL keywords for identifier names. #17526 (Alexey Milovidov).
• Allow query parameters in UPDATE statement of ALTER query. Fixes #10976. #17563 (Alexey Milovidov).
• Don't throw "Too many parts" error in the middle of INSERT query. #17566 (Alexey Milovidov).
• Allow to reload symbols from debug file. This PR also fixes a build-id issue. #17637 (Amos Bird).
• This fixes #17457. #17641 (Nikita Mikhaylov).
• Switch to patched version of RocksDB (from ClickHouse-Extras). #17643 (Nikita Mikhaylov).
• Do not ignore server memory limits during Buffer flush. #17646 (Azat Khuzhin).
• Removed exception throwing at table initialization if there was no connection (it will be reconnecting in the background). #17709 (Kseniia Sumarokova).
• system.query_log now has extensive information to achieve better query analysis. #17726 (Amos Bird).
• Check system log tables' engine definition grammatically to prevent some configuration errors. Notes that this grammar check is not semantical, that means such mistakes as non-existent columns / expression functions would be not found out util the table is created. #17739 (Du Chuan).
• Improves the path concatenation of zookeeper paths inside DDLWorker. #17767 (Bharat Nallan).
• Improvement of Web UI: do not add empty query to browser history. #17770 (Alexey Milovidov).
• • Let the possibility to override timeout value for running script using the ClickHouse docker image. #17818 (Guillaume Tassery).
• Add metrics(Parts, PartsActive, PartsInactive) for part number in MergeTree in clickhouse. #17838 (徐炘).
• Add diagnostic information when two merge tables try to read each other's data. #17854 (徐炘).
• Hints for column names. #17112. #17857 (fastio).
• Support for async tasks in PipelineExecutor. Initial support of async sockets for remote queries. #17868 (Nikolai Kochetov).
• allow_introspection_functions=0 prohibits usage of introspection functions but doesn't prohibit giving grants for them anymore (the grantee will need to set allow_introspection_functions=1 for himself to be able to use that grant). Similarly allow_ddl=0 prohibits usage of DDL commands but doesn't prohibit giving grants for them anymore. #17908 (Vitaly Baranov).
• Ability to set custom metadata when putting S3 object. #17909 (Pavel Kovalenko).
• Adaptive choose of single/multi part upload in WriteBufferFromS3. Single part upload is controlled by a new setting 'max_single_part_upload_size'. #17934 (Pavel Kovalenko).
• Forcibly removing empty or bad metadata files from filesystem for DiskS3. S3 is an experimental feature. #17935 (Pavel Kovalenko).
• Now the table function merge() requires the current user to have the SELECT privilege on each table it receives data from. This PR fixes #16964. #17983 (Vitaly Baranov).
• Decrease log verbosity of the events when the client drops the connection from WARNING to INFORMATION. #18005 (filimonov).
• Fix clickhouse-client rendering issue when the size of terminal window changes. #18009 (Amos Bird).
• Temporary tables are visible in the system tables system.tables and system.columns now only in those session where they have been created. The internal database _temporary_and_external_tables is now hidden in those system tables; temporary tables are shown as tables with empty database with the is_temporary flag set instead. #18014 (Vitaly Baranov).
• Fix dead list watches removal for TestKeeperStorage. #18065 (alesapin).
• Support SHOW CREATE VIEW name syntax like MySQL. #18095 (Du Chuan).
• Now the table function merge() requires the current user to have the SELECT privilege on each table it receives data from. This PR fixes #16964. #18104 (Vitaly Baranov).
• Add disk to Set and Join storage settings. #18112 (Pervakov Grigorii).
• EXPLAIN AST now support queries other then SELECT. #18136 (李扬).
• All queries of type Decimal * Float or vice versa are allowed, including aggregate ones (e.g. SELECT sum(decimal_field * 1.1) or SELECT dec_col * float_col), the result type is Float32 or Float64. #18145 (Mike Kot).
• Array aggregation arrayMin, arrayMax, arraySum, arrayAvg support for Int128, Int256, UInt256. #18147 (Maksim Kita).
• Better hints for SHOW ... query syntax. #18183 (Du Chuan).
• Now clickhouse-install could work on Mac. The problem was that there is no procfs on this platform. #18201 (Nikita Mikhaylov).
• Make better adaptive granularity calculation for merge tree wide parts. #18223 (alesapin).
• Allow to parse Array fields from CSV if it is represented as a string containing array that was serialized as nested CSV. Example: "[""Hello"", ""world"", ""42"""" TV""]" will parse as ['Hello', 'world', '42" TV']. Allow to parse array in CSV in a string without enclosing braces. Example: "'Hello', 'world', '42"" TV'" will parse as ['Hello', 'world', '42" TV']. #18271 (Alexey Milovidov).
• In case of unexpected exceptions automatically restart background thread which is responsible for execution of distributed DDL queries. Fixes #17991. #18285 (徐炘).
• Add a new setting insert_distributed_one_random_shard = 1 to allow insertion into multi-sharded distributed table without any distributed key. #18294 (Amos Bird).
• related to #18133. #18309 (hexiaoting).
• Fix potential server crash during Buffer rollback (that is impossible in current ClickHouse version). #18329 (Azat Khuzhin).
• Support builtin function isIPv4String && isIPv6String like MySQL. #18349 (Du Chuan).
• Add ability to modify primary and partition key column type from LowCardinality(Type) to Type and vice versa. Also add an ability to modify primary key column type from EnumX to IntX type. Fixes #5604. #18362 (alesapin).
• Fix bug: no newline after exception message in some tools. #18444 (Alexey Milovidov).
• support syntax EXISTS DATABASE name. #18458 (Du Chuan).
• Fixed assertion error inside allocator in case when last argument of function bar is NaN. Now simple ClickHouse's exception is being thrown. This fixes #17876. #18520 (Nikita Mikhaylov).
• PODArray: Avoid call to memcpy with (nullptr, 0) arguments (Fix UBSan report). This fixes #18525. #18526 (Alexey Milovidov).
• Fix SimpleAggregateFunction in SummingMergeTree. Now it works like AggregateFunction. In previous versions values were summed together regardless to the aggregate function. This fixes #18564 . #8052. #18637 (Amos Bird).
• Another fix of using SimpleAggregateFunction in SummingMergeTree. This fixes #18676 . #18677 (Amos Bird).
• Allow column transformer EXCEPT to accept a string as regular expression matcher. This resolves #18685 . #18699 (Amos Bird).
• Apply ALTER TABLE <replicated_table> ON CLUSTER MODIFY SETTING ... to all replicas. Because we don't replicate such alter commands. #18789 (Amos Bird).
• Expand macros in the zk path when executing fetchPartition. #18839 (fastio).
• SYSTEM KILL command started to work in Docker. This closes #18847. #18848 (Alexey Milovidov).
• Two new settings (by analogy with MergeTree family) has been added: - fsync_after_insert - Do fsync for every inserted. Will decreases performance of inserts. - fsync_directories - Do fsync for temporary directory (that is used for async INSERT only) after all operations (writes, renames, etc.). #18864 (Azat Khuzhin).
• change the sorting key of events_list from timestamp to (timestamp, event_index). #18884 (Fuwang Hu).
• Aliases declared in WITH statement are properly used in index analysis. Queries like WITH column AS alias SELECT ... WHERE alias = ... may use index now. #18896 (Amos Bird).

Bug Fix

• Fix bug when clickhouse-server doesn't send close request to ZooKeeper server. #16837 (alesapin).
• TODO. #16866 (Alexander Tokmakov).
• Fix optimization of group by with enabled setting optimize_aggregators_of_group_by_keys and joins. Fixes #12604. #16951 (Anton Popov).
• Fix incorrect comparison of types DateTime64 with different scales. Fixes #16655 ... #16952 (Vasily Nemkov).
• Fix order by optimization with monotonous functions. Fixes #16107. #16956 (Anton Popov).
• Fix Merge(Distributed()) with JOIN. #16993 (Azat Khuzhin).
• • Fix optimize_distributed_group_by_sharding_key for query with OFFSET only. #16996 (Azat Khuzhin).
• Bug fix for funciton fuzzBits, related issue: #16980. #17051 (hexiaoting).
• Fix possible wrong index analysis when the types of the index comparison are different. This fixes #17122. #17145 (Amos Bird).
• Fixed possible not-working mutations for parts stored on S3 disk. #17227 (Pavel Kovalenko).
• Fix #15235. When clickhouse-copier handle non-partitioned table, throws segfault error. #17248 (Qi Chen).
• Fix set index invalidation when there are const columns in the subquery. This fixes #17246 . #17249 (Amos Bird).
• Fix possible Unexpected packet Data received from client error for Distributed queries with LIMIT. #17254 (Azat Khuzhin).
• Fix indeterministic functions with predicate optimizer. This fixes #17244. #17273 (Winter Zhang).
• fixes #16835 try fix miss match header with MySQL SHOW statement. #17366 (Winter Zhang).
• Fix crash while reading from JOIN table with LowCardinality types. Fixes #17228. #17397 (Nikolai Kochetov).
• Fixed high CPU usage in background tasks of *MergeTree tables. #17416 (Alexander Tokmakov).
• Fix duplicates after DISTINCT which were possible because of incorrect optimization. Fixes #17294. #17296 (li chengxiang). #17439 (Nikolai Kochetov).
• Avoid server abnormal termination in case of too low memory limits (max_memory_usage=1/max_untracked_memory=1). #17453 (Azat Khuzhin).
• Fix ORDER BY with enabled setting optimize_redundant_functions_in_order_by. #17471 (Anton Popov).
• Fix bug when mark cache size was underestimated by clickhouse. It may happen when there are a lot of tiny files with marks. #17496 (alesapin).
• Fix alter query hang when the corresponding mutation was killed on the different replica. Fixes #16953. #17499 (alesapin).
• Fix the issue when server can stop accepting connections in very rare cases. #17542 (Alexey Milovidov).
• When clickhouse-client is used in interactive mode with multiline queries, single line comment was erronously extended till the end of query. This fixes #13654. #17565 (Alexey Milovidov).
• Exception fmt::v7::format_error can be logged in background for MergeTree tables. This fixes #17613. #17615 (Alexey Milovidov).
• Fix empty system.stack_trace table when server is running in daemon mode. #17630 (Amos Bird).
• In might be determined incorrectly if cluster is circular- (cross-) replicated or not when executing ON CLUSTER query due to race condition when pool_size > 1. It's fixed. #17640 (Alexander Tokmakov).
• Fixed Function not implemented error when executing RENAME query in Atomic database with ClickHouse running on Windows Subsystem for Linux. Fixes #17661. #17664 (Alexander Tokmakov).
• Fixed problem when ClickHouse fails to resume connection to MySQL servers. #17681 (Alexander Kazakov).
• Fixed segfault when there is not enough space when inserting into Distributed table. #17737 (Alexander Tokmakov).
• Exception message about max table size to drop was displayed incorrectly. #17764 (Alexey Milovidov).
• Do not restore parts from WAL if in_memory_parts_enable_wal is disabled. #17802 (detailyang).
• fix incorrect initialize max_compress_block_size of MergeTreeWriterSettings with min_compress_block_size. #17833 (flynn).
• Fix possible segfault in topK aggregate function. This closes #17404. #17845 (Maksim Kita).
• Fix max_distributed_connections (affects prefer_localhost_replica=1 and max_threads!=max_distributed_connections). #17848 (Azat Khuzhin).
• Trivial query optimization was producing wrong result if query contains ARRAY JOIN (so query is actually non trivial). #17887 (sundyli).
• Fix comparison of DateTime64 and Date. Fixes #13804 and #11222. ... #17895 (Vasily Nemkov).
• When server log rotation was configured using logger.size parameter with numeric value larger than 2^32, the logs were not rotated properly. This is fixed. #17905 (Alexander Kuzmenkov).
• fixes #15187 fixes #17912 support convert MySQL prefix index for MaterializeMySQL CC: @tavplubix. #17944 (Winter Zhang).
• Fix comparison of DateTime64 and Date. Fixes #13804 and #11222. ... #18050 (Vasily Nemkov).
• Fix corruption in librdkafka snappy decompression (was a problem only for gcc10 builds, but official builds uses clang already, so at least recent official releases are not affected). #18053 (Azat Khuzhin).
• Fixed std::out_of_range: basic_string in S3 URL parsing. #18059 (Vladimir Chebotarev).
• Fix error when query MODIFY COLUMN ... REMOVE TTL doesn't actually remove column TTL. #18130 (alesapin).
• Fix Unknown setting profile error on attempt to set settings profile. #18167 (Alexander Tokmakov).
• Fix inserting a row with default value in case of parsing error in the last column. Fixes #17712. #18182 (Jianmei Zhang).
• fixes #18186 fixes #16372 fix unique key convert crash in MaterializeMySQL database engine. #18211 (Winter Zhang).
• Fix key comparison between Enum and Int types. This fixes #17989. #18214 (Amos Bird).
• Fix possible incomplete query result while reading from MergeTree* in case of read backoff (message <Debug> MergeTreeReadPool: Will lower number of threads in logs). Was introduced in #16423. Fixes #18137. #18216 (Nikolai Kochetov).
• SELECT JOIN now requires the SELECT privilege on each of the joined tables. This PR fixes #17654. #18232 (Vitaly Baranov).
• • Fixed issue when clickhouse-odbc-bridge process is unreachable by server on machines with dual IPv4/IPv6 stack; - Fixed issue when ODBC dictionary updates are performed using malformed queries and/or cause crashes; Possibly closes #14489. #18278 (Denis Glazachev).
• Fix possible crashes in aggregate functions with combinator Distinct, while using two-level aggregation. Fixes #17682. #18365 (Anton Popov).
• Fix filling table system.settings_profile_elements. This PR fixes #18231. #18379 (Vitaly Baranov).
• Restrict merges from wide to compact parts. In case of vertical merge it led to broken result part. #18381 (Anton Popov).
• Fix possible race condition in concurrent usage of Set or Join tables and selects from system.tables. #18385 (Alexey Milovidov).
• Fix -SimpleState combinator generates incompatible arugment type and return type. #18404 (Amos Bird).
• Fix the unexpected behaviour of SHOW TABLES. #18431 (fastio).
• Fixed value is too short error when executing toType(...) functions (toDate, toUInt32, etc) with argument of type Nullable(String). Now such functions return NULL on parsing errors instead of throwing exception. Fixes #7673. #18445 (Alexander Tokmakov).
• Proper support for 12AM in parseDateTimeBestEffort function. This fixes #18402. #18449 (vladimir-golovchenko).
• Disable write with AIO during merges because it can lead to extremely rare data corruption of primary key columns during merge. #18481 (alesapin).
• Fix bug which may lead to ALTER queries hung after corresponding mutation kill. Found by thread fuzzer. #18518 (alesapin).
• Fix possible Pipeline stuck error while using ORDER BY after subquery with RIGHT or FULL join. #18550 (Nikolai Kochetov).
• Add FixedString Data type support. I'll get this exception "Code: 50, e.displayText() = DB::Exception: Unsupported type FixedString(1)" when replicating data from MySQL to ClickHouse. This patch fixes bug #18450 Also fixes #6556. #18553 (awesomeleo).
• Fix previous bug when date overflow with different values. Strict Date value limit to "2106-02-07", cast date > "2106-02-07" to value 0. #18565 (hexiaoting).
• Fix removing of empty parts in ReplicatedMergeTree tables, created with old syntax. Fixes #18582. #18614 (Anton Popov).
• Fix Logger with unmatched arg size. #18717 (sundyli).
• Fixed Attempt to read after eof error when trying to CAST NULL from Nullable(String) to Nullable(Decimal(P, S)). Now function CAST returns NULL when it cannot parse decimal from nullable string. Fixes #7690. #18718 (Winter Zhang).
• Asynchronous distributed INSERTs can be rejected by the server if the setting network_compression_method is globally set to non-default value. This fixes #18741. #18776 (Alexey Milovidov).
• Fix *If combinator with unary function and Nullable types. #18806 (Azat Khuzhin).
• • Fix never worked fsync_part_directory/fsync_after_insert/in_memory_parts_insert_sync. #18845 (Azat Khuzhin).
• Fix use after free bug in rocksdb. #18862 (sundyli).
• Queries for external databases (MySQL, ODBC, JDBC) were incorrectly rewritten if there was an expression in form of x IN table. This fixes #9756. #18876 (Alexey Milovidov).
• Fix possible hang at shutdown in clickhouse-local. This fixes #18891. #18893 (Alexey Milovidov).
• Fix issue with bitmapOrCardinality that may lead to nullptr dereference. This closes #18911. #18912 (sundyli).

Build/Testing/Packaging Improvement

• Add some test for MaterializeMySQL. e.g. network partition, MySQL kill sync thread... #16806 (TCeason).
• Now ClickHouse can pretend to be a fake ZooKeeper. Currently, storage implementation is just stored in-memory hash-table, and server partially support ZooKeeper protocol. #16877 (alesapin).
• • Added RBAC tests for ATTACH, CREATE, DROP, and DETACH. #16977 (MyroTk).
• PODArray does not initialize "new" elements when resizing, unlike std::vector. This probably fixes this failure from #17309. #17344 (Nikita Mikhaylov).
• There was an uninitialized variable in the code of Copier. #17363 (Nikita Mikhaylov).
• Send info about official build, memory, cpu and free disk space to Sentry if it is enabled. Sentry is opt-in feature to help ClickHouse developers. This closes #17279. #17543 (Alexey Milovidov).
• Add an integration test: MySQL server killed while insert for MaterializeMySQL Engine. #17614 (TCeason).
• Add an integration test: ClickHouse killed while insert for MaterializeMySQL ENGINE. #17622 (TCeason).
• • RBAC testflows tests for SHOW, TRUNCATE, KILL, and OPTIMIZE. - Updates to old tests. - Resolved comments from #https://github.com/ClickHouse/ClickHouse/pull/16977. #17657 (MyroTk).
• Now we use the fresh docker daemon version in integration tests. #17671 (alesapin).
• • Testflows tests for RBAC ACCESS MANAGEMENT privileges. #17804 (MyroTk).
• Updating TestFlows README.md to include "How To Debug Why Test Failed" section. #17808 (vzakaznikov).
• Add our own CMakeList for dragonbox which was added in #17831. #17869 (Nikita Mikhaylov).
• Enable Pytest framework for stateless tests. #17902 (Ivan).
• Adjusting timeouts a bit, in the good hope that it will prevent flakiness of the test. #18000 (filimonov).
• Now, clickhouse-test DROP/CREATE databases with a timeout. #18098 (alesapin).
• Change OpenSSL to BoringSSL. It allows to avoid issues with sanitizers. This fixes #12490. This fixes #17502. This fixes #12952. #18129 (Alexey Milovidov).
• Fix usage of uninitialized value in function toModifiedJulianDayOrNull, reported by MSan. Was discovered here. #18172 (Nikita Mikhaylov).
• Update anchore/scan-action@main workflow action (was moved from master). #18192 (Stig Bakken).
• Do not use non thread-safe function strerror. #18204 (Alexey Milovidov).
• • Updating TestFlows version to the latest 1.6.72 - Re-generating requirements.py. #18208 (vzakaznikov).
• Merging requirements for AES encryption functions. Updating aes_encryption tests to use new requirements. Updating TestFlows version to 1.6.72. #18221 (vzakaznikov).
• Enable Thread Fuzzer for stateless tests flaky check. #18299 (alesapin).
• Check for leftovers of conflict markers in docs. #18332 (Alexey Milovidov).
• Fix codespell warnings. Split style checks into separate parts. Update style checks docker image. #18463 (Ilya Yatsishin).
• Update timezones info to 2020e. #18531 (alesapin).
• Fix shellcheck errors in style check. #18566 (Ilya Yatsishin).
• TestFlows: fixes to LDAP tests that fail due to slow test execution. #18790 (vzakaznikov).
• Generate build id when ClickHouse is linked with lld. It's appeared that lld does not generate it by default on my machine. Build id is used for crash reports and introspection. #18808 (Alexey Milovidov).
• Add simple integrity check for ClickHouse binary. It allows to detect corruption due to faulty hardware (bit rot on storage media or bit flips in RAM). #18811 (Alexey Milovidov).
• Removed the -finline-hint-functions flag not present in GCC. #18846 (Mike Kot).
• Add SYSTEM SUSPEND command for fault injection. It can be used to faciliate failover tests. This closes #15979. #18850 (Alexey Milovidov).

NO CL ENTRY

• NO CL ENTRY: 'Bump mkdocs-macros-plugin from 0.4.20 to 0.5.0 in /docs/tools'. #17351 (dependabot-preview[bot]).
• NO CL ENTRY: 'Revert "Attempt to fix Stress test (MSan)"'. #17372 (Nikita Mikhaylov).
• NO CL ENTRY: 'Revert "Bump mkdocs-macros-plugin from 0.4.20 to 0.5.0 in /docs/tools"'. #17405 (Alexey Milovidov).
• NO CL ENTRY: 'Update README.md'. #17596 (Robert Hodges).
• NO CL ENTRY: 'Revert "Fix index granularity calculation on block borders"'. #17918 (alesapin).
• NO CL ENTRY: 'Revert "Date vs DateTime64 comparison"'. #17985 (Alexey Milovidov).
• NO CL ENTRY: 'Исправил опечатку в названии ОС RedHad->RedHat'. #18028 (Ed Rakhmankulov).
• NO CL ENTRY: 'Revert "Fix access rights required for the merge() table function."'. #18103 (Alexey Milovidov).
• NO CL ENTRY: 'Revert "Add some extra tests to copier"'. #18636 (Nikita Mikhaylov).
• NO CL ENTRY: 'Fix typo in array functions' documentation'. #18792 (Bertrand Junqua).
• NO CL ENTRY: 'Revert "Add metrics for part number in MergeTree in ClickHouse"'. #18834 (Alexey Milovidov).
• NO CL ENTRY: 'Fixed typo in metrics.md'. #18920 (Mark Frost).