Things

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

@@ -16,6 +16,7 @@ Columns:
 - `next_refresh_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Time at which the next refresh is scheduled to start.
 - `remaining_dependencies` ([Array(String)](../../sql-reference/data-types/array.md)) — If the view has [refresh dependencies](../../sql-reference/statements/create/view.md#refresh-dependencies), this array contains the subset of those dependencies that are not satisfied for the current refresh yet. If `status = 'WaitingForDependencies'`, a refresh is ready to start as soon as these dependencies are fulfilled.
 - `exception` ([String](../../sql-reference/data-types/string.md)) — if `last_refresh_result = 'Exception'`, i.e. the last refresh attempt failed, this column contains the corresponding error message and stack trace.
+- `refresh_count` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Number of successful refreshes since last server restart or table creation.
 - `progress` ([Float64](../../sql-reference/data-types/float.md)) — Progress of the current refresh, between 0 and 1.
 - `read_rows` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Number of rows read by the current refresh so far.
 - `total_rows` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Estimated total number of rows that need to be read by the current refresh.

docs/en/sql-reference/statements/create/view.md

@@ -130,7 +130,7 @@ Currently refreshable materialized views require [Atomic database engine](../../
 
 Example refresh schedules:
 ```sql
-REFRESH EVERY 1 DAY -- every day, at midnight
+REFRESH EVERY 1 DAY -- every day, at midnight (UTC)
 REFRESH EVERY 1 MONTH -- on 1st day of every month, at midnight
 REFRESH EVERY 1 MONTH OFFSET 5 DAY 2 HOUR -- on 6th day of every month, at 2:00 am
 REFRESH EVERY 2 WEEK OFFSET 5 DAY 15 HOUR 10 MINUTE -- every other Saturday, at 3:10 pm
@@ -181,6 +181,10 @@ A few more examples:
  * `REFRESH AFTER 1 HOUR` depends on `REFRESH AFTER 1 HOUR`<br/>
    Currently this is not recommended.
 
+:::note
+`DEPENDS ON` only works between refreshable materialized views. Listing a regular table in the `DEPENDS ON` list will prevent the view from ever refreshing (dependencies can be reomoved with `ALTER`, see below).
+:::
+
 ### Changing Refresh Parameters {#changing-refresh-parameters}
 
 To change refresh parameters:

src/Common/CalendarTimeInterval.cpp

@@ -136,4 +136,9 @@ bool CalendarTimeInterval::operator==(const CalendarTimeInterval & rhs) const
     return std::tie(months, seconds) == std::tie(rhs.months, rhs.seconds);
 }
 
+bool CalendarTimeInterval::operator!=(const CalendarTimeInterval & rhs) const
+{
+    return !(*this == rhs);
+}
+
 }

src/Common/CalendarTimeInterval.h

@@ -57,6 +57,7 @@ struct CalendarTimeInterval
     std::chrono::sys_seconds floor(std::chrono::system_clock::time_point t) const;
 
     bool operator==(const CalendarTimeInterval & rhs) const;
+    bool operator!=(const CalendarTimeInterval & rhs) const;
 };
 
 }

src/Databases/DatabasesCommon.cpp

@@ -65,6 +65,11 @@ void applyMetadataChangesToCreateQuery(const ASTPtr & query, const StorageInMemo
         query->replace(ast_create_query.select, metadata.select.select_query);
     }
 
+    if (metadata.refresh)
+    {
+        query->replace(ast_create_query.refresh_strategy, metadata.refresh);
+    }
+
     /// MaterializedView, Dictionary are types of CREATE query without storage.
     if (ast_create_query.storage)
     {

src/Processors/Executors/ManualPipelineExecutor.cpp

@@ -38,7 +38,7 @@ ManualPipelineExecutor::~ManualPipelineExecutor()
     }
     catch (...)
     {
-        tryLogCurrentException("ManualPipelineExecutor");
+        tryLogCurrentException(__PRETTY_FUNCTION__);
     }
 }
 

src/Storages/AlterCommands.cpp

@@ -742,7 +742,7 @@ void AlterCommand::apply(StorageInMemoryMetadata & metadata, ContextPtr context)
     }
     else if (type == MODIFY_REFRESH)
     {
-        metadata.refresh = metadata.refresh->clone();
+        metadata.refresh = refresh->clone();
     }
     else if (type == MODIFY_SETTING)
     {

src/Storages/MaterializedView/RefreshSchedule.cpp

@@ -18,7 +18,7 @@ RefreshSchedule::RefreshSchedule(const ASTRefreshStrategy & strategy)
 bool RefreshSchedule::operator!=(const RefreshSchedule & rhs) const
 {
     static_assert(sizeof(*this) == 7*8, "If fields were added or removed in RefreshSchedule, please update this comparator.");
-    return std::tie(kind, period, offset, spread) == std::tie(rhs.kind, rhs.period, rhs.offset, rhs.spread);
+    return std::tie(kind, period, offset, spread) != std::tie(rhs.kind, rhs.period, rhs.offset, rhs.spread);
 }
 
 static std::chrono::sys_seconds advanceEvery(std::chrono::system_clock::time_point prev, CalendarTimeInterval period, CalendarTimeInterval offset)

src/Storages/MaterializedView/RefreshSet.cpp

@@ -73,7 +73,7 @@ void RefreshSet::Handle::reset()
 
 RefreshSet::RefreshSet() = default;
 
-RefreshSet::Handle RefreshSet::emplace(StorageID id, std::vector<StorageID> dependencies, RefreshTaskHolder task)
+RefreshSet::Handle RefreshSet::emplace(StorageID id, const std::vector<StorageID> & dependencies, RefreshTaskHolder task)
 {
     std::lock_guard guard(mutex);
     auto [it, is_inserted] = tasks.emplace(id, task);

src/Storages/MaterializedView/RefreshSet.h

@@ -35,6 +35,7 @@ struct RefreshInfo
     LastRefreshResult last_refresh_result = LastRefreshResult::Unknown;
     std::optional<UInt32> last_refresh_time;
     UInt32 next_refresh_time = 0;
+    UInt64 refresh_count = 0;
     String exception_message; // if last_refresh_result is Exception
     std::vector<StorageID> remaining_dependencies;
     ProgressValues progress;
@@ -80,7 +81,7 @@ public:
 
     RefreshSet();
 
-    Handle emplace(StorageID id, std::vector<StorageID> dependencies, RefreshTaskHolder task);
+    Handle emplace(StorageID id, const std::vector<StorageID> & dependencies, RefreshTaskHolder task);
 
     RefreshTaskHolder getTask(const StorageID & id) const;
 

src/Storages/MaterializedView/RefreshTask.cpp

@@ -73,11 +73,10 @@ void RefreshTask::alterRefreshParams(const DB::ASTRefreshStrategy & new_strategy
         for (auto && dependency : new_strategy.dependencies->children)
             deps.emplace_back(dependency->as<const ASTTableIdentifier &>());
 
-    refresh_schedule = new_schedule;
-
     /// Reschedule next refresh.
     if (new_schedule != refresh_schedule)
     {
+        refresh_schedule = new_schedule;
         next_refresh_prescribed = {};
         advanceNextRefreshTime(currentTime());
         refresh_task->schedule();
@@ -93,7 +92,8 @@ void RefreshTask::alterRefreshParams(const DB::ASTRefreshStrategy & new_strategy
         if (!deps_set.contains(id))
             removed_deps.push_back(id);
     for (const auto & id : removed_deps)
-        arriveDependency(id);
+        if (arriveDependency(id) && !std::exchange(refresh_immediately, true))
+            refresh_task->schedule();
 
     /// TODO: Update settings once we have them.
 }
@@ -180,7 +180,7 @@ void RefreshTask::shutdown()
     set_handle.reset();
 }
 
-void RefreshTask::notify(const StorageID & parent_id, std::chrono::sys_seconds prescribed_time, const RefreshSchedule & parent_schedule)
+void RefreshTask::notify(const StorageID & parent_id, std::chrono::sys_seconds parent_next_prescribed_time, const RefreshSchedule & parent_schedule)
 {
     std::lock_guard guard(mutex);
     if (!set_handle)
@@ -218,7 +218,7 @@ void RefreshTask::notify(const StorageID & parent_id, std::chrono::sys_seconds p
     /// Only accept the dependency's refresh if its next refresh time is after ours.
     /// This takes care of cases (1)-(4), and seems harmless in all other cases.
     /// Might be mildly helpful in weird cases like REFRESH AFTER 3 HOUR depends on REFRESH AFTER 2 HOUR.
-    if (parent_schedule.prescribeNext(prescribed_time, currentTime()) <= next_refresh_prescribed)
+    if (parent_next_prescribed_time <= next_refresh_prescribed)
         return;
 
     if (arriveDependency(parent_id) && !std::exchange(refresh_immediately, true))
@@ -334,7 +334,6 @@ void RefreshTask::refreshTask()
             info.state = RefreshState::Running;
 
             CurrentMetrics::Increment metric_inc(CurrentMetrics::RefreshingViews);
-            auto prescribed_time = next_refresh_prescribed;
 
             lock.unlock();
 
@@ -348,9 +347,7 @@ void RefreshTask::refreshTask()
                 finished = executeRefreshUnlocked();
 
                 if (finished)
-                    completeRefreshUnlocked(view, prescribed_time);
+                    completeRefreshUnlocked(view);
-
-                lock.lock();
             }
             catch (...)
             {
@@ -360,7 +357,7 @@ void RefreshTask::refreshTask()
                 LOG_ERROR(log, message);
 
                 /// Don't leave a trash table.
-                if (!finished && refresh_context)
+                if (refresh_context)
                     cancelRefreshUnlocked();
 
                 lock.lock();
@@ -369,19 +366,32 @@ void RefreshTask::refreshTask()
                 info.exception_message = text;
 
                 /// TODO: Do a few retries with exponential backoff.
-                if (!finished)
                 advanceNextRefreshTime(currentTime());
-            }
-            chassert(lock.owns_lock());
 
-            if (finished)
+                continue;
-            {
+            }
+
+            lock.lock();
+
+            if (!finished)
+                continue;
+
             auto now = currentTime();
             auto secs = std::chrono::floor<std::chrono::seconds>(now);
             info.last_refresh_time = UInt32(secs.time_since_epoch().count());
             info.last_refresh_result = LastRefreshResult::Finished;
+            info.refresh_count += 1;
             advanceNextRefreshTime(now);
-            }
+
+            auto next_time = next_refresh_prescribed;
+            auto refresh_schedule_copy = refresh_schedule;
+
+            lock.unlock();
+            StorageID my_id = view->getStorageID();
+            auto dependents = view->getContext()->getRefreshSet().getDependents(my_id);
+            for (const RefreshTaskHolder & dep_task : dependents)
+                dep_task->notify(my_id, next_time, refresh_schedule_copy);
+            lock.lock();
         }
     }
     catch (...)
@@ -427,24 +437,13 @@ bool RefreshTask::executeRefreshUnlocked()
     return finished;
 }
 
-void RefreshTask::completeRefreshUnlocked(std::shared_ptr<StorageMaterializedView> view, std::chrono::sys_seconds prescribed_time)
+void RefreshTask::completeRefreshUnlocked(std::shared_ptr<StorageMaterializedView> view)
 {
     auto stale_table = view->exchangeTargetTable(refresh_query->table_id, refresh_context);
-
     auto refresh_context_ptr_copy = refresh_context;
     cleanStateUnlocked();
 
-    std::unique_lock lock(mutex);
+    InterpreterDropQuery::executeDropQuery(ASTDropQuery::Kind::Drop, view->getContext(), refresh_context_ptr_copy, stale_table, /*sync*/ true, /*ignore_sync_setting*/ true);
-    auto refresh_schedule_copy = refresh_schedule;
-    lock.unlock();
-
-    auto global_context = view->getContext();
-    StorageID my_id = view->getStorageID();
-    auto dependents = global_context->getRefreshSet().getDependents(my_id);
-    for (const RefreshTaskHolder & dep_task : dependents)
-        dep_task->notify(my_id, prescribed_time, refresh_schedule_copy);
-
-    InterpreterDropQuery::executeDropQuery(ASTDropQuery::Kind::Drop, global_context, refresh_context_ptr_copy, stale_table, /*sync*/ true, /*ignore_sync_setting*/ true);
 }
 
 void RefreshTask::cancelRefreshUnlocked()

src/Storages/MaterializedView/RefreshTask.h

@@ -62,7 +62,7 @@ public:
     void shutdown();
 
     /// Notify dependent task
-    void notify(const StorageID & parent_id, std::chrono::sys_seconds prescribed_time, const RefreshSchedule & parent_schedule);
+    void notify(const StorageID & parent_id, std::chrono::sys_seconds parent_next_prescribed_time, const RefreshSchedule & parent_schedule);
 
     void setFakeTime(std::optional<Int64> t);
 
@@ -145,7 +145,7 @@ private:
     void initializeRefreshUnlocked(std::shared_ptr<const StorageMaterializedView> view);
     bool executeRefreshUnlocked();
     /// Whoever calls complete/cancelRefreshUnlocked() should also assign info.last_refresh_result.
-    void completeRefreshUnlocked(std::shared_ptr<StorageMaterializedView> view, std::chrono::sys_seconds prescribed_time);
+    void completeRefreshUnlocked(std::shared_ptr<StorageMaterializedView> view);
     void cancelRefreshUnlocked();
     void cleanStateUnlocked();
 

src/Storages/System/StorageSystemViewRefreshes.cpp

@@ -24,6 +24,7 @@ NamesAndTypesList StorageSystemViewRefreshes::getNamesAndTypes()
         {"next_refresh_time", std::make_shared<DataTypeDateTime>()},
         {"remaining_dependencies", std::make_shared<DataTypeArray>(std::make_shared<DataTypeString>())},
         {"exception", std::make_shared<DataTypeString>()},
+        {"refresh_count", std::make_shared<DataTypeUInt64>()},
         {"progress", std::make_shared<DataTypeFloat64>()},
         {"elapsed", std::make_shared<DataTypeFloat64>()},
         {"read_rows", std::make_shared<DataTypeUInt64>()},
@@ -68,6 +69,7 @@ void StorageSystemViewRefreshes::fillData(
         res_columns[i++]->insert(Array(deps));
 
         res_columns[i++]->insert(refresh.exception_message);
+        res_columns[i++]->insert(refresh.refresh_count);
         res_columns[i++]->insert(Float64(refresh.progress.read_rows) / refresh.progress.total_rows_to_read);
         res_columns[i++]->insert(refresh.progress.elapsed_ns / 1e9);
         res_columns[i++]->insert(refresh.progress.read_rows);

tests/queries/0_stateless/02932_refreshable_materialized_views.reference

@@ -1,5 +1,42 @@
-a	[]		1
+<1: created view>	a	[]		1
-CREATE MATERIALIZED VIEW <db>a\nREFRESH AFTER 1 SECOND\n(\n    `x` UInt64\n)\nENGINE = Memory AS\nSELECT number\nFROM numbers(2)\nUNION ALL\nSELECT rand64()
+CREATE MATERIALIZED VIEW default.a\nREFRESH AFTER 1 SECOND\n(\n    `x` UInt64\n)\nENGINE = Memory AS\nSELECT number AS x\nFROM numbers(2)\nUNION ALL\nSELECT rand64() AS x
-3	1	1
+<2: refreshed>	3	1	1
-500
+<3: time difference at least>	500
-1
+<4: next refresh in>	1
+CREATE MATERIALIZED VIEW default.a\nREFRESH EVERY 2 YEAR\n(\n    `x` Int16\n)\nENGINE = Memory AS\nSELECT x * 2 AS x\nFROM default.src
+<5: no refresh>	3
+<6: refreshed>	2
+<7: refreshed>	Scheduled	Finished	2054-01-01 00:00:00
+CREATE MATERIALIZED VIEW default.b\nREFRESH EVERY 2 YEAR DEPENDS ON default.a\n(\n    `y` Int32\n)\nENGINE = MergeTree\nORDER BY y\nSETTINGS index_granularity = 8192 AS\nSELECT x * 10 AS y\nFROM default.a
+<8: refreshed>	20
+<9: refreshed>	a	Scheduled	Finished	2054-01-01 00:00:00
+<9: refreshed>	b	Scheduled	Finished	2054-01-01 00:00:00
+<10: waiting>	a	Scheduled	[]	2054-01-01 00:00:00
+<10: waiting>	b	WaitingForDependencies	['default.a']	2054-01-01 00:00:00
+<11: chain-refreshed a>	4
+<12: chain-refreshed b>	40
+<13: chain-refreshed>	a	Scheduled	[]	Finished	2054-01-01 00:00:01	2056-01-01 00:00:00	
+<13: chain-refreshed>	b	Scheduled	['default.a']	Finished	2054-01-24 23:22:21	2056-01-01 00:00:00	
+<14: waiting for next cycle>	a	Scheduled	[]	2058-01-01 00:00:00
+<14: waiting for next cycle>	b	WaitingForDependencies	['default.a']	2060-01-01 00:00:00
+<15: chain-refreshed a>	6
+<16: chain-refreshed b>	60
+<17: chain-refreshed>	a	Scheduled	2062-01-01 00:00:00
+<17: chain-refreshed>	b	Scheduled	2062-01-01 00:00:00
+<18: removed dependency>	b	Scheduled	[]	2062-03-03 03:03:03	2064-01-01 00:00:00	5
+CREATE MATERIALIZED VIEW default.b\nREFRESH EVERY 2 YEAR\n(\n    `y` Int32\n)\nENGINE = MergeTree\nORDER BY y\nSETTINGS index_granularity = 8192 AS\nSELECT x * 10 AS y\nFROM default.a
+<19: exception>	1
+<20: unexception>	1
+<21: rename>	1
+<22: rename>	d	Finished
+<23: simple refresh>	1
+<24: rename during refresh>	1
+<25: rename during refresh>	f	Running
+<26: paused+resumed>	1
+<27: canceled>	f	Scheduled
+CREATE MATERIALIZED VIEW default.g\nREFRESH EVERY 1 WEEK OFFSET 3 DAY 4 HOUR RANDOMIZE FOR 4 DAY 1 HOUR\n(\n    `x` Int64\n)\nENGINE = Memory AS\nSELECT 42
+<29: randomize>	1	1
+CREATE MATERIALIZED VIEW default.h\nREFRESH EVERY 1 SECOND TO default.dest\n(\n    `x` Int64\n) AS\nSELECT x * 10 AS x\nFROM default.src
+<30: to existing table>	10
+<31: to existing table>	10
+<31: to existing table>	20

tests/queries/0_stateless/02932_refreshable_materialized_views.sh

@@ -7,7 +7,7 @@ CLICKHOUSE_LOG_COMMENT=
 # shellcheck source=../shell_config.sh
 . "$CUR_DIR"/../shell_config.sh
 
-$CLICKHOUSE_CLIENT -nq "drop table if exists refreshes; drop table if exists a;"
+CLICKHOUSE_CLIENT="`echo "$CLICKHOUSE_CLIENT" | sed 's/--session_timezone[= ][^ ]*//g'`"
 
 $CLICKHOUSE_CLIENT -nq "create view refreshes as select * from system.view_refreshes where database = '$CLICKHOUSE_DATABASE' order by view"
 
@@ -17,16 +17,16 @@ $CLICKHOUSE_CLIENT -nq "
     create materialized view a
         refresh after 1 second (x UInt64)
         engine Memory
-        as select number from numbers(2) union all select rand64()"
+        as select number as x from numbers(2) union all select rand64() as x"
-$CLICKHOUSE_CLIENT -nq "select view, remaining_dependencies, exception, last_refresh_result in ('Unknown', 'Finished') from refreshes";
+$CLICKHOUSE_CLIENT -nq "select '<1: created view>', view, remaining_dependencies, exception, last_refresh_result in ('Unknown', 'Finished') from refreshes";
-$CLICKHOUSE_CLIENT -nq "show create a" | sed "s/$CLICKHOUSE_DATABASE./<db>/"
+$CLICKHOUSE_CLIENT -nq "show create a"
-# Wait for any refresh.
+# Wait for any refresh. (xargs trims the string and turns \t and \n into spaces)
 while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" == 'Unknown' ]
 do
     sleep 0.1
 done
 # Check table contents.
-$CLICKHOUSE_CLIENT -nq "select count(), sum(x=0), sum(x=1) from a"
+$CLICKHOUSE_CLIENT -nq "select '<2: refreshed>', count(), sum(x=0), sum(x=1) from a"
 # Wait for table contents to change.
 res1="`$CLICKHOUSE_CLIENT -nq 'select * from a order by x format Values'`"
 while :
@@ -35,7 +35,7 @@ do
     [ "$res2" == "$res1" ] || break
     sleep 0.1
 done
-time2="`$CLICKHOUSE_CLIENT -nq \"select reinterpret(now64(), 'Int64')\"`"
+time2="`$CLICKHOUSE_CLIENT -nq "select reinterpret(now64(), 'Int64')"`"
 # Wait for another change.
 while :
 do
@@ -43,12 +43,257 @@ do
     [ "$res3" == "$res2" ] || break
     sleep 0.1
 done
-time3="`$CLICKHOUSE_CLIENT -nq \"select reinterpret(now64(), 'Int64')\"`"
 # Check that the two changes were at least 500ms apart, in particular that we're not refreshing
 # like crazy. This is potentially flaky, but we need at least one test that uses non-mocked timer
 # to make sure the clock+timer code works at all. If it turns out flaky, increase refresh period above.
 $CLICKHOUSE_CLIENT -nq "
-    select min2($time3-$time2, 500);
+    select '<3: time difference at least>', min2(reinterpret(now64(), 'Int64') - $time2, 500);
-    select next_refresh_time-last_refresh_time from refreshes;"
+    select '<4: next refresh in>', next_refresh_time-last_refresh_time from refreshes;"
 
-$CLICKHOUSE_CLIENT -nq "drop table refreshes; drop table a;"
+# Create a source table from which views will read.
+$CLICKHOUSE_CLIENT -nq "
+    create table src (x Int8) engine Memory as select 1"
+
+# Switch to fake clock, change refresh schedule, change query.
+$CLICKHOUSE_CLIENT -nq "
+    system test view a set fake time '2050-01-01 00:00:01';
+    alter table a modify refresh every 2 year;
+    alter table a modify query select x*2 as x from src;"
+$CLICKHOUSE_CLIENT -nq "show create a"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status, next_refresh_time from refreshes" | xargs`" != 'Scheduled 2052-01-01 00:00:00' ]
+do
+    sleep 0.1
+done
+# Advance time to trigger the refresh.
+$CLICKHOUSE_CLIENT -nq "
+    select '<5: no refresh>', count() from a;
+    system test view a set fake time '2052-02-03 04:05:06';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_time from refreshes" | xargs`" != '2052-02-03 04:05:06' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<6: refreshed>', * from a;
+    select '<7: refreshed>', status, last_refresh_result, next_refresh_time from refreshes;"
+
+# Create a dependent view, refresh it once.
+$CLICKHOUSE_CLIENT -nq "
+    create materialized view b refresh every 2 year depends on a (y Int32) engine MergeTree order by y as select x*10 as y from a;
+    show create b;
+    system test view b set fake time '2052-11-11 11:11:11';
+    system refresh view b;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_time from refreshes where view = 'b'" | xargs`" != '2052-11-11 11:11:11' ]
+do
+    sleep 0.1
+done
+# Next refresh shouldn't start until the dependency refreshes.
+$CLICKHOUSE_CLIENT -nq "
+    select '<8: refreshed>', * from b;
+    select '<9: refreshed>', view, status, last_refresh_result, next_refresh_time from refreshes;
+    system test view b set fake time '2054-01-24 23:22:21';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status, next_refresh_time from refreshes where view = 'b'" | xargs`" != 'WaitingForDependencies 2054-01-01 00:00:00' ]
+do
+    sleep 0.1
+done
+# Update source table (by dropping and re-creating it - to test that tables are looked up by name
+# rather than uuid), kick off refresh of the dependency.
+$CLICKHOUSE_CLIENT -nq "
+    select '<10: waiting>', view, status, remaining_dependencies, next_refresh_time from refreshes;
+    drop table src;
+    create table src (x Int16) engine Memory as select 2;
+    system test view a set fake time '2054-01-01 00:00:01';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes where view = 'b'" | xargs`" != 'Scheduled' ]
+do
+    sleep 0.1
+done
+# Both tables should've refreshed.
+$CLICKHOUSE_CLIENT -nq "
+    select '<11: chain-refreshed a>', * from a;
+    select '<12: chain-refreshed b>', * from b;
+    select '<13: chain-refreshed>', view, status, remaining_dependencies, last_refresh_result, last_refresh_time, next_refresh_time, exception from refreshes;"
+
+# Make the dependent table run ahead by one refresh cycle, make sure it waits for the dependency to
+# catch up to the same cycle.
+$CLICKHOUSE_CLIENT -nq "
+    system test view b set fake time '2059-01-01 00:00:00';
+    system refresh view b;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select next_refresh_time from refreshes where view = 'b'" | xargs`" != '2060-01-01 00:00:00' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    system test view b set fake time '2061-01-01 00:00:00';
+    system test view a set fake time '2057-01-01 00:00:00';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status, next_refresh_time from refreshes" | xargs`" != 'Scheduled 2058-01-01 00:00:00 WaitingForDependencies 2060-01-01 00:00:00' ]
+do
+    sleep 0.1
+done
+sleep 1
+$CLICKHOUSE_CLIENT -nq "
+    select '<14: waiting for next cycle>', view, status, remaining_dependencies, next_refresh_time from refreshes;
+    truncate src;
+    insert into src values (3);
+    system test view a set fake time '2060-02-02 02:02:02';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select next_refresh_time from refreshes where view = 'b'" | xargs`" != '2062-01-01 00:00:00' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<15: chain-refreshed a>', * from a;
+    select '<16: chain-refreshed b>', * from b;
+    select '<17: chain-refreshed>', view, status, next_refresh_time from refreshes;"
+
+# Get to WaitingForDependencies state and remove the depencency.
+$CLICKHOUSE_CLIENT -nq "
+    system test view b set fake time '2062-03-03 03:03:03'"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes where view = 'b'" | xargs`" != 'WaitingForDependencies' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    alter table b modify refresh every 2 year"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status, last_refresh_time from refreshes where view = 'b'" | xargs`" != 'Scheduled 2062-03-03 03:03:03' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<18: removed dependency>', view, status, remaining_dependencies, last_refresh_time,next_refresh_time, refresh_count from refreshes where view = 'b';
+    show create b;"
+
+# Select from a table that doesn't exist, get an exception.
+$CLICKHOUSE_CLIENT -nq "
+    drop table a;
+    drop table b;
+    create materialized view c refresh every 1 second (x Int64) engine Memory as select * from src;
+    drop table src;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" != 'Exception' ]
+do
+    sleep 0.1
+done
+# Check exception, create src, expect successful refresh.
+$CLICKHOUSE_CLIENT -nq "
+    select '<19: exception>', exception ilike '%table%src%exist%UNKNOWN_TABLE%' from refreshes;
+    create table src (x Int64) engine Memory as select 1;
+    system refresh view c;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" != 'Finished' ]
+do
+    sleep 0.1
+done
+# Rename table.
+$CLICKHOUSE_CLIENT -nq "
+    select '<20: unexception>', * from c;
+    rename table c to d;
+    select '<21: rename>', * from d;
+    select '<22: rename>', view, last_refresh_result from refreshes;"
+
+# Do various things during a refresh.
+# First make a nonempty view.
+$CLICKHOUSE_CLIENT -nq "
+    drop table d;
+    truncate src;
+    insert into src values (1)
+    create materialized view e refresh every 1 second (x Int64) engine MergeTree order by x as select x + sleepEachRow(1) as x from src settings max_block_size = 1;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" != 'Finished' ]
+do
+    sleep 0.1
+done
+# Stop refreshes.
+$CLICKHOUSE_CLIENT -nq "
+    select '<23: simple refresh>', * from e;
+    system stop view e;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes" | xargs`" != 'Disabled' ]
+do
+    sleep 0.1
+done
+# Make refreshes slow, make for a slow refresh to start. (We stopped refreshes first to make sure
+# we wait for a slow refresh, not a previous fast one.)
+$CLICKHOUSE_CLIENT -nq "
+    insert into src select * from numbers(1000) settings max_block_size=1;
+    system start view e;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes" | xargs`" != 'Running' ]
+do
+    sleep 0.1
+done
+# Rename.
+$CLICKHOUSE_CLIENT -nq "
+    rename table e to f;
+    select '<24: rename during refresh>', * from f;
+    select '<25: rename during refresh>', view, status from refreshes;
+    alter table f modify refresh after 10 year;"
+sleep 2 # make it likely that at least one row was processed
+# Pause.
+rows_before_pause="`$CLICKHOUSE_CLIENT -nq "select read_rows from refreshes" | xargs`"
+$CLICKHOUSE_CLIENT -nq "
+    system pause view f;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes" | xargs`" != 'Paused' ]
+do
+    sleep 0.1
+done
+# Resume.
+$CLICKHOUSE_CLIENT -nq "
+    system resume view f;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes" | xargs`" != 'Running' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<26: paused+resumed>', read_rows >= $rows_before_pause from refreshes"
+# Cancel.
+$CLICKHOUSE_CLIENT -nq "
+    system cancel view f;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" != 'Canceled' ]
+do
+    sleep 0.1
+done
+# Check that another refresh doesn't immediately start after the canceled one.
+sleep 1
+$CLICKHOUSE_CLIENT -nq "
+    select '<27: canceled>', view, status from refreshes;
+    system refresh view f;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select status from refreshes" | xargs`" != 'Running' ]
+do
+    sleep 0.1
+done
+# Drop.
+$CLICKHOUSE_CLIENT -nq "
+    drop table f;
+    select '<28: drop during refresh>', view, status from refreshes;"
+
+# Try OFFSET and RANDOMIZE FOR.
+$CLICKHOUSE_CLIENT -nq "
+    create materialized view g refresh every 1 week offset 3 day 4 hour randomize for 4 day 1 hour (x Int64) engine Memory as select 42;
+    show create g;
+    system test view g set fake time '2050-02-03 15:30:13';"
+while [ "`$CLICKHOUSE_CLIENT -nq "select next_refresh_time > '2049-01-01' from refreshes" | xargs`" != '1' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    with '2050-02-10 04:00:00'::DateTime as expected
+    select '<29: randomize>', abs(next_refresh_time::Int64 - expected::Int64) <= 3600*(24*4+1), next_refresh_time != expected from refreshes;"
+
+# Send data 'TO' an existing table.
+$CLICKHOUSE_CLIENT -nq "
+    drop table g;
+    create table dest (x Int64) engine MergeTree order by x;
+    truncate src;
+    insert into src values (1);
+    create materialized view h refresh every 1 second to dest as select x*10 as x from src;
+    show create h;"
+while [ "`$CLICKHOUSE_CLIENT -nq "select last_refresh_result from refreshes" | xargs`" != 'Finished' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<30: to existing table>', * from dest;
+    insert into src values (2);"
+while [ "`$CLICKHOUSE_CLIENT -nq "select count() from dest" | xargs`" != '2' ]
+do
+    sleep 0.1
+done
+$CLICKHOUSE_CLIENT -nq "
+    select '<31: to existing table>', * from dest;
+    drop table dest;
+    drop table src;
+    drop table h;
+    drop table refreshes;"