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use LowCardinality for _file and _path virtual columns in StorageFile #34317

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merged 1 commit into from
Feb 4, 2022

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@ucasfl ucasfl commented Feb 4, 2022

Changelog category (leave one):

  • Performance Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
_file and _path virtual columns (in file-like table engines) are made LowCardinality - it will make queries for multiple files faster. Closes #34300

@robot-clickhouse robot-clickhouse added the pr-not-for-changelog This PR should not be mentioned in the changelog label Feb 4, 2022
@robot-clickhouse robot-clickhouse added pr-performance Pull request with some performance improvements and removed pr-not-for-changelog This PR should not be mentioned in the changelog labels Feb 4, 2022
@alexey-milovidov alexey-milovidov self-assigned this Feb 4, 2022
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alexey-milovidov commented Feb 4, 2022

Ok.

There are no new tests. But performance tests will be difficult to construct.
I hope that _path and _file are already covered by previous tests.

@alexey-milovidov alexey-milovidov merged commit e194bf3 into ClickHouse:master Feb 4, 2022
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@ucasfl I forgot to say that we have other similar cases - s3, hdfs, etc. Grep by "_path".
Let's do it for all of them.

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ucasfl commented Feb 5, 2022

@ucasfl I forgot to say that we have other similar cases - s3, hdfs, etc. Grep by "_path". Let's do it for all of them.

OK, I will do it.

ucasfl added a commit to ucasfl/ClickHouse that referenced this pull request Feb 5, 2022
ucasfl added a commit to ucasfl/ClickHouse that referenced this pull request Feb 6, 2022
alexey-milovidov added a commit that referenced this pull request Feb 6, 2022
use LowCardinality type for _file and _path in some Storages, continue of #34317
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_path virtual column should be LowCardinality
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