Use AsyncPipelineExecutor all dictionaries #55839

vdimir · 2023-10-19T14:51:49Z

Changelog category (leave one):

Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

All dictionaries support setting dictionary_use_async_executor

Documentation entry for user-facing changes

Documentation is written (mandatory for new features)

robot-ch-test-poll2 · 2023-10-19T14:53:22Z

This is an automated comment for commit 8bc384e with description of existing statuses. It's updated for the latest CI running

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nickitat · 2023-10-23T12:48:37Z

docs/en/operations/settings/settings.md

+SOURCE(CLICKHOUSE(QUERY `SELECT key, attr FROM t1 GROUP BY key`))
+LIFETIME(MIN 0 MAX 3600)
+LAYOUT(COMPLEX_KEY_HASHED_ARRAY())
+SETTINGS(dictionary_use_async_executor=1, max_threads=8);


not clear how many threads will be used if I wouldn't specify max_threads

It should be a default behavior (with max_threads=0 or 'auto' and set to the number of cpus). Let me recheck it.

UPD: behavior is the same as for regular query, max_threads set automatically

nickitat · 2023-10-23T12:51:54Z

docs/en/operations/settings/settings.md

+SOURCE(CLICKHOUSE(QUERY `SELECT key, attr FROM t1 GROUP BY key`))
+LIFETIME(MIN 0 MAX 3600)
+LAYOUT(COMPLEX_KEY_HASHED_ARRAY())
+SETTINGS(dictionary_use_async_executor=1, max_threads=8);


why someone could want to not use async executor?

When the query itself is more lightweight that dictionary filling. To consume less query by executing source query and not to spawn additional threads. But if we will realize that it's always beneficial we may set it by default if a future.

nickitat · 2023-10-23T12:53:39Z

src/Dictionaries/DictionarySourceHelpers.cpp

+    else if (executor)
+        return executor->pull(block);
+    else
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "DictionaryPipelineExecutor is not initialized");


maybe let's do it straight in the ctor?

In ctor it's clear that one of executors is initialized from initializer-list. I added this branch just in case if new ctor is added and there it may be forgotten.

nickitat · 2023-10-23T12:56:33Z

src/Dictionaries/DictionarySourceHelpers.cpp

+        while (true)
+        {
+            bool has_data = async_executor->pull(block);
+            if (has_data && !block)


why we don't skip empty blocks when pulling from sync executor?

Sync executor never returns them. Actually Async shouldn't do it either. Perhaps this fix can help #55945 , but not sure it that is correct and complete fix.

nickitat · 2023-10-23T13:06:22Z

src/Dictionaries/RegExpTreeDictionary.cpp

        const auto dict_id = StorageID::fromDictionaryConfig(config, config_prefix);

        auto context = copyContextAndApplySettingsFromDictionaryConfig(global_context, config, config_prefix);
+        const auto * clickhouse_source = typeid_cast<const ClickHouseDictionarySource *>(source_ptr.get());


why here it is typeid_cast?

As far as class ClickHouseDictionarySource final it shouldn't be any difference between typeid_cast and dynamic_cast

robot-ch-test-poll2 added the pr-improvement Pull request with some product improvements label Oct 19, 2023

nickitat self-assigned this Oct 19, 2023

vdimir added 2 commits October 19, 2023 15:16

Use AsyncPipelineExecutor for HashedArrayDictionary

0ece6e0

Use AsyncPipelineExecutor for reading clickhouse dictionary source

b4851cf

vdimir force-pushed the vdimir/async_executor_for_dictionary_load branch from 78848fd to b4851cf Compare October 19, 2023 15:16

vdimir added 2 commits October 20, 2023 12:30

Handle empty block in DictionaryPipelineExecutor

1aa4a54

More dictionaries support dictionary_use_async_executor

8bc384e

vdimir changed the title ~~Use AsyncPipelineExecutor for HashedArrayDictionary~~ Use AsyncPipelineExecutor all dictionaries Oct 20, 2023

vdimir requested a review from nickitat October 23, 2023 09:29

nickitat reviewed Oct 23, 2023

View reviewed changes

vdimir merged commit da6f334 into master Oct 24, 2023
298 checks passed

vdimir deleted the vdimir/async_executor_for_dictionary_load branch October 24, 2023 09:31

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Use AsyncPipelineExecutor all dictionaries #55839

Use AsyncPipelineExecutor all dictionaries #55839

vdimir commented Oct 19, 2023 •

edited

robot-ch-test-poll2 commented Oct 19, 2023 •

edited by robot-ch-test-poll1

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Use AsyncPipelineExecutor all dictionaries #55839

Use AsyncPipelineExecutor all dictionaries #55839

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vdimir commented Oct 19, 2023 • edited

Changelog category (leave one):

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Documentation entry for user-facing changes

robot-ch-test-poll2 commented Oct 19, 2023 • edited by robot-ch-test-poll1

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vdimir commented Oct 19, 2023 •

edited

robot-ch-test-poll2 commented Oct 19, 2023 •

edited by robot-ch-test-poll1