Optimize queries with LIMIT/LIMIT BY/ORDER BY for distributed with GROUP BY sharding_key by azat · Pull Request #10373 · ClickHouse/ClickHouse

azat · 2020-04-20T08:24:00Z

Changelog category (leave one):

Performance Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Optimize queries with LIMIT/LIMIT BY/ORDER BY for distributed with GROUP BY sharding_key (under optimize_skip_unused_shards and optimize_distributed_group_by_sharding_key)

Detailed description / Documentation draft:

Previous set of QueryProcessingStage does not allow to do this.

So this patch set introduces new WithMergeableStateAfterAggregation and use
it to optimize queries with GROUP BY sharding_key and:

LIMIT
LIMIT BY
ORDER BY

And right now it is still not supports:

WITH TOTALS (looks like it can be supported)
WITH ROLLUP (looks like it can be supported)
WITH CUBE
SETTINGS extremes=1 (looks like it can be supported)

Details

HEAD:

6c4748a63e7acde2cc3283d96ffec590aae1e724 (initial)
a2467f205f4ab120443afbb426cec3d5a506478d (with ABI breakage)
348ef1256ea8fb8f61109c33bbdd28daf46bdc8e (worked)

Continuation of:

azat · 2020-04-25T21:06:50Z

So to summarize this should solve some issues that had been introduced by the #10341 and adds support for LIMIT/LIMIT BY/ORDER BY

azat · 2020-08-15T21:35:29Z

AST fuzzer — Assertion `(n >= (static_cast<ssize_t>(pad_left_) ? -1 : 0)) && (n <= static_cast<ssize_t>(this->size()))' failed

#13790

azat · 2020-08-16T21:55:27Z

Performance — Timeout :(

@akuzm can you please take a look is it false-positive or not? (or maybe I should just restart the build? by i.e. rebasing against upstream/master)

src/Core/QueryProcessingStage.h

azat · 2020-08-17T13:46:13Z

@akuzm can you please take a look is it false-positive or not? (or maybe I should just restart the build? by i.e. rebasing against upstream/master)

Never mind, the problem is in the protocol ABI breakage (queries like select * from system.numbers limit 1 via python clickhouse client works forever, because of the wrong processing stage)

azat · 2020-08-18T18:11:50Z

@4ertus2 this is ready, can you take a look?

azat · 2020-08-18T18:28:46Z

Functional stateless tests (debug) — fail: 1, passed: 2168, skipped: 14

The 00956_sensitive_data_masking is flacky (#13867 )

azat · 2020-08-27T08:52:38Z

@4ertus2 @alexey-milovidov friendly ping, can some one take a look?

azat · 2020-08-27T23:43:37Z

Functional stateless tests (unbundled) — fail: 1, passed: 2156, skipped: 50

2020-08-27 23:43:34 01085_max_distributed_connections:                                      [ FAIL ] 2.00 sec. - return code 124
2020-08-27 23:43:34 , result:
2020-08-27 23:43:34 
2020-08-27 23:43:34 0
2020-08-27 23:43:34 0
2020-08-27 23:43:34

So here we got the result already, but timeout triggers (timeout exists with 124 if the timeout reached)
Fix this by increasing the delay (as long as number of remote streams) - #14199

azat · 2020-08-31T18:30:17Z

@alexey-milovidov any thoughts on this?

Process query until the stage where the aggregate functions were calculated and finalized. It will be used for optimize_distributed_group_by_sharding_key. v2: fix aliases v3: Fix protocol ABI breakage due to WithMergeableStateAfterAggregation Conditions >= for QueryProcessingStage::Enum has been verified, and they are ok (in InterpreterSelectQuery).

…OUP BY sharding_key Previous set of QueryProcessingStage does not allow to do this. But after WithMergeableStateAfterAggregation had been introduced the following queries can be optimized too under optimize_distributed_group_by_sharding_key: - GROUP BY sharding_key LIMIT - GROUP BY sharding_key LIMIT BY - GROUP BY sharding_key ORDER BY And right now it is still not supports: - WITH TOTALS (looks like it can be supported) - WITH ROLLUP (looks like it can be supported) - WITH CUBE - SETTINGS extremes=1 (looks like it can be supported) But will be implemented separatelly. vX: fixes v2: fix WITH * v3: fix extremes v4: fix LIMIT OFFSET (and make a little bit cleaner) v5: fix HAVING v6: fix ORDER BY v7: rebase against 20.7 v8: move out WithMergeableStateAfterAggregation v9: add optimize_distributed_group_by_sharding_key into test names

…merge (convert to UInt64) Possible values: - 1 - Do not merge aggregation states from different servers for distributed query processing - in case it is for certain that there are different keys on different shards. - 2 - same as 1 but also apply ORDER BY and LIMIT stages

azat · 2020-09-02T21:55:37Z

Yandex synchronization check (only for Yandex employees)

rebased in attempt to fix it

tests/queries/0_stateless/arcadia_skip_list.txt

alexey-milovidov · 2020-09-03T01:33:50Z

tests/queries/0_stateless/01247_optimize_distributed_group_by_sharding_key_dist_on_dist.sql

 drop table if exists dist_01247;
 drop table if exists dist_layer_01247;

 select 'Distributed(rand)-over-Distributed(rand)';
 create table dist_layer_01247 as data_01247 engine=Distributed(test_cluster_two_shards, currentDatabase(), data_01247, rand());
 create table dist_01247 as data_01247 engine=Distributed(test_cluster_two_shards, currentDatabase(), dist_layer_01247, number);
-select count(), * from dist_01247 group by number;
-drop table dist_01247;


Don't understand this change, will return DROP queries...

When test DROP TABLE at the end you cannot attach with the client and reproduce the failure, that's why I'm trying to keep them, so that said that this is just a cosmetic thing.
@alexey-milovidov Is there some unspoken rule that said that tables should be removed after the test?

It's just for convenience when you run .sql files manually and don't want leftovers.

alexey-milovidov

LGTM.

I understand the logic. It looks a bit fragile because StorageDistributed should maintain its awareness of all possible pipeline steps after GROUP BY. It is Ok but we need to write randomized combinatoral tests for correctness of Distributed tables on various types of clusters.

alexey-milovidov · 2020-09-03T01:47:33Z

tests/queries/0_stateless/00184_shard_distributed_group_by_no_merge.sql

@@ -1,2 +1,42 @@
-SELECT count(), uniq(dummy) FROM remote('127.0.0.{2,3}', system.one) SETTINGS distributed_group_by_no_merge = 1;


I'd better add new test instead of modifying an old simple test case.

azat · 2020-09-03T22:05:34Z

Performance — 4 faster, 5 slower, 449 unstable

FWIW here is previous test report (before rebase against upstream/master) - https://clickhouse-test-reports.s3.yandex.net/10373/9e4aa5954e45865d7756e1a6a174d7c1cf0ccfa0/performance_comparison/report.html#fail1
And it does not have those slow downs.

blinkov added the pr-improvement Pull request with some product improvements label Apr 20, 2020

azat force-pushed the dist-SELECT-optimization branch from 253a3f8 to aaab84b Compare April 22, 2020 08:03

azat changed the title ~~[WIP] Avoid some stages for distributed queries whenever it is possible~~ More optimizations for distributed with GROUP BY sharding_key Apr 22, 2020

azat force-pushed the dist-SELECT-optimization branch from aaab84b to f56560d Compare April 22, 2020 08:10

azat marked this pull request as draft April 22, 2020 19:42

azat force-pushed the dist-SELECT-optimization branch from f56560d to c9fa74b Compare April 22, 2020 21:46

azat changed the title ~~More optimizations for distributed with GROUP BY sharding_key~~ Optimize queries with LIMIT/LIMIT BY/ORDER BY for distributed with GROUP BY sharding_key Apr 22, 2020

azat marked this pull request as ready for review April 22, 2020 21:47

azat force-pushed the dist-SELECT-optimization branch from c9fa74b to 296b2fb Compare April 22, 2020 21:54

azat marked this pull request as draft April 25, 2020 19:38

azat force-pushed the dist-SELECT-optimization branch 2 times, most recently from 95f7af3 to d417da3 Compare April 25, 2020 21:04

azat marked this pull request as ready for review April 25, 2020 21:05

azat marked this pull request as draft April 26, 2020 00:19

azat mentioned this pull request Apr 26, 2020

Disable GROUP BY sharding_key optimization by default (and fix for WITH ROLLUP/CUBE/TOTALS) #10516

Merged

4ertus2 self-assigned this May 25, 2020

alexey-milovidov force-pushed the master branch from 6c77191 to 09b9a30 Compare June 9, 2020 02:04

4ertus2 removed their assignment Jul 9, 2020

azat force-pushed the dist-SELECT-optimization branch 3 times, most recently from 6c4748a to a2467f2 Compare August 15, 2020 17:02

azat marked this pull request as ready for review August 15, 2020 17:04

azat commented Aug 17, 2020

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src/Core/QueryProcessingStage.h Outdated Show resolved Hide resolved

azat force-pushed the dist-SELECT-optimization branch from a2467f2 to 348ef12 Compare August 17, 2020 18:36

azat mentioned this pull request Aug 20, 2020

Auto distributed_group_by_no_merge on GROUP BY sharding key #10341

Merged

azat force-pushed the dist-SELECT-optimization branch from 348ef12 to f39f2c5 Compare August 25, 2020 18:09

azat force-pushed the dist-SELECT-optimization branch from f39f2c5 to cc6fb4f Compare August 27, 2020 19:03

azat added 5 commits September 3, 2020 00:51

Add a test for distributed_group_by_no_merge=2

5e71fe3

Add documentation for optimize_distributed_group_by_sharding_key

776688a

azat force-pushed the dist-SELECT-optimization branch from cc6fb4f to 776688a Compare September 2, 2020 21:54

azat commented Sep 2, 2020

View reviewed changes

tests/queries/0_stateless/arcadia_skip_list.txt Show resolved Hide resolved

robot-clickhouse added pr-performance Pull request with some performance improvements and removed pr-improvement Pull request with some product improvements labels Sep 3, 2020

alexey-milovidov reviewed Sep 3, 2020

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alexey-milovidov self-assigned this Sep 3, 2020

Update StorageDistributed.cpp

edea940

alexey-milovidov approved these changes Sep 3, 2020

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alexey-milovidov added 3 commits September 3, 2020 04:45

Update 01247_optimize_distributed_group_by_sharding_key_dist_on_dist.sql

722e1bb

Update 01247_optimize_distributed_group_by_sharding_key.sql

06edd21

Update 00184_shard_distributed_group_by_no_merge.sql

9e4aa59

alexey-milovidov reviewed Sep 3, 2020

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alexey-milovidov merged commit 4f9df21 into ClickHouse:master Sep 3, 2020

azat deleted the dist-SELECT-optimization branch September 3, 2020 22:45

azat mentioned this pull request Jun 15, 2021

Customizable query block for distributed engine. #5986

Closed

		@@ -1,2 +1,42 @@
		SELECT count(), uniq(dummy) FROM remote('127.0.0.{2,3}', system.one) SETTINGS distributed_group_by_no_merge = 1;

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