CI reports failure of the 01442_merge_detach_attach test [1]:
<details>
2021-06-21 02:25:43 01442_merge_detach_attach: [ FAIL ] 122.37 sec. - result differs with reference:
2021-06-21 02:25:43 --- /usr/share/clickhouse-test/queries/0_stateless/01442_merge_detach_attach.reference 2021-06-21 00:43:12.000000000 +0300
2021-06-21 02:25:43 +++ /tmp/clickhouse-test/0_stateless/01442_merge_detach_attach.stdout 2021-06-21 02:25:43.211212197 +0300
2021-06-21 02:25:43 @@ -0,0 +1 @@
2021-06-21 02:25:43 +2
2021.06.21 02:25:08.930896 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Debug> executeQuery: (from [::1]:36540, using production parser) (comment: '/usr/share/clickhouse-test/queries/0_stateless/01442_merge_detach_attach.sh') ALTER TABLE t DETACH PARTITION tuple()
2021.06.21 02:25:08.931245 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> executeQuery: (from [::1]:36542, using production parser) (comment: '/usr/share/clickhouse-test/queries/0_stateless/01442_merge_detach_attach.sh') OPTIMIZE TABLE t FINAL
2021.06.21 02:25:08.931826 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Trace> ContextAccess (default): Access granted: ALTER DELETE ON test_89nl0v.t
2021.06.21 02:25:08.932159 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Trace> ContextAccess (default): Access granted: OPTIMIZE ON test_89nl0v.t
2021.06.21 02:25:08.932889 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Information> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249): Detaching all_143_143_0
2021.06.21 02:25:08.932921 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Selected 2 parts from all_143_143_0 to all_144_144_0
2021.06.21 02:25:08.933530 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> DiskLocal: Reserving 1.00 MiB on disk `default`, having unreserved 4.60 TiB.
2021.06.21 02:25:08.933705 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Information> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249): Detaching all_144_144_0
2021.06.21 02:25:08.934215 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Merging 2 parts: from all_143_143_0 to all_144_144_0 into Compact
2021.06.21 02:25:08.934280 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Information> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249): Detached 2 parts.
2021.06.21 02:25:08.934948 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Selected MergeAlgorithm: Horizontal
2021.06.21 02:25:08.936090 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> MergeTreeSequentialSource: Reading 2 marks from part all_143_143_0, total 1 rows starting from the beginning of the part, column x
2021.06.21 02:25:08.937621 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> MergeTreeSequentialSource: Reading 2 marks from part all_144_144_0, total 1 rows starting from the beginning of the part, column x
2021.06.21 02:25:08.938124 [ 100543 ] {16eb4fe5-2d6b-4c81-a6be-c6a3b293edd3} <Debug> MemoryTracker: Peak memory usage (for query): 0.00 B.
2021.06.21 02:25:08.939928 [ 100543 ] {} <Debug> TCPHandler: Processed in 0.018537432 sec.
2021.06.21 02:25:08.942140 [ 100543 ] {} <Debug> TCPHandler: Done processing connection.
2021.06.21 02:25:08.948343 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Merge sorted 2 rows, containing 1 columns (1 merged, 0 gathered) in 0.014203821 sec., 140.80718139154246 rows/sec., 140.81 B/sec.
2021.06.21 02:25:08.952021 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Trace> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249): Renaming temporary part tmp_merge_all_143_144_1 to all_143_144_1.
2021.06.21 02:25:08.952869 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Warning> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Unexpected number of parts removed when adding all_143_144_1: 0 instead of 2
2021.06.21 02:25:08.953264 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Trace> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (MergerMutator): Merged 2 parts: from all_143_143_0 to all_144_144_0
2021.06.21 02:25:08.953913 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> MemoryTracker: Peak memory usage: 4.01 MiB.
2021.06.21 02:25:08.958369 [ 100540 ] {bd4b710d-cd27-44ea-9dc9-e45d6ace0bd7} <Debug> MemoryTracker: Peak memory usage (for query): 4.01 MiB.
...
2021.06.21 02:25:09.216075 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> executeQuery: (from [::1]:36544, using production parser) (comment: '/usr/share/clickhouse-test/queries/0_stateless/01442_merge_detach_attach.sh') SELECT count() FROM t HAVING count() > 0
2021.06.21 02:25:09.229491 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Trace> ContextAccess (default): Access granted: SELECT(x) ON test_89nl0v.t
2021.06.21 02:25:09.232000 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Trace> InterpreterSelectQuery: FetchColumns -> Complete
2021.06.21 02:25:09.239907 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (SelectExecutor): Key condition: unknown
2021.06.21 02:25:09.240358 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> test_89nl0v.t (efd364af-6721-4249-afd3-64af67214249) (SelectExecutor): Selected 1/1 parts by partition key, 1 parts by primary key, 1/1 marks by primary key, 1 marks to read from 1 ranges
2021.06.21 02:25:09.241560 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> MergeTreeSelectProcessor: Reading 1 ranges from part all_143_144_1, approx. 2 rows starting from 0
2021.06.21 02:25:09.256053 [ 58403 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Trace> AggregatingTransform: Aggregating
2021.06.21 02:25:09.256410 [ 58403 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Trace> Aggregator: Aggregation method: without_key
2021.06.21 02:25:09.257576 [ 58403 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> AggregatingTransform: Aggregated. 2 to 1 rows (from 2.00 B) in 0.013910412 sec. (143.777 rows/sec., 143.78 B/sec.)
2021.06.21 02:25:09.257911 [ 58403 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Trace> Aggregator: Merging aggregated data
2021.06.21 02:25:09.262595 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Information> executeQuery: Read 2 rows, 2.00 B in 0.045805192 sec., 43 rows/sec., 43.66 B/sec.
2021.06.21 02:25:09.263337 [ 100543 ] {1699b404-b132-4b96-b04a-1c28cd062a79} <Debug> MemoryTracker: Peak memory usage (for query): 0.00 B.
</details>
[1]: https://clickhouse-test-reports.s3.yandex.net/25513/b96df135aee40b1a54a4fc3f0d4db89e11385564/functional_stateless_tests_(memory).html#fail1
The problem here is that there is a tiny race window between DETACH
and OPTIMIZE.
DETACH cancel merges, and checks that there no merges for parts
currently under lock, and later changes the state of parts. After it
allows merges.
However OPTIMIZE get parts for processing under lock and only when it
starts writing temporary part it checks that merges are not canceled.
So suppose the following scenario:
T#OPTIMIZE T#DETACH
- cancel merges
- lock
- check that no merges are in progress
- unlock
- lock
- get parts
*<--Here, state of the parts are not changed yet,
and lock is not held,
so OPTIMIZE may (and will) get those parts. -->*
- write temporary part
- check merges not canceled
- unlock
- change the parts state
- allows merges
Plus this patch will also fail merges earlier in case of concurrent
DETACH.
Refs: #13746
Refs: #23315
Before this patch KILL MUTATION marks mutation as canceled just by name
(and part numbers) so if you have multiple tables with the same part
name, then killing mutation for one table, will mark it as killed for
another too.
Fix this by comparing StorageID too (it is better to use StorageID over
database/table to avoid ambiguity by using UUIDs for comparing).
Here is a failure of the 01414_freeze_does_not_prevent_alters on CI [1].
[1]: https://clickhouse-test-reports.s3.yandex.net/24069/9fb69dcf98c71a939d200cad3c8491bf43a44622/functional_stateless_tests_(ubsan).html#fail1
TODO (suggested by Nikolai)
1. Build query plan fro current query (inside storage::read) up to WithMergableState
2. Check, that plan is simple enough: Aggregating - Expression - Filter - ReadFromStorage (or simplier)
3. Check, that filter is the same as filter in projection, and also expression calculates the same aggregation keys as in projection
4. Return WithMergableState if projection applies
3 will be easier to do with ActionsDAG, cause it sees all functions, and dependencies are direct (but it is possible with ExpressionActions also)
Also need to figure out how prewhere works for projections, and
row_filter_policies.
wip
In a busy system without enough threads to process mutations at the moment,
you would get a log message per data part with pending mutations, which in
some extreme cases could be dozens per call.
