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Optimize SortPreservingMergeStream to avoid SortKeyCursor sharing #1624

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merged 13 commits into from
Jan 22, 2022
Merged

Optimize SortPreservingMergeStream to avoid SortKeyCursor sharing #1624

merged 13 commits into from
Jan 22, 2022

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yjshen
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@yjshen yjshen commented Jan 21, 2022 •
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Which issue does this PR close?

This PR is based on #1596 so please review that one first.

Rationale for this change

In SortPreservingMergeStream, SortKeyCursor shouldn't be shared between min_heap and output batch buffer. The current sharing leads to the use of AtomicUsize, which may harm performance.

What changes are included in this PR?

  • Use RecordBatch instead of SortKeyCursor for output batch buffering.
  • Add a per-stream flag cursor_finished to make sure each input stream is pulled after a resume from Pending.
  • Remove AtomicUsize from SortKeyCursor.

Are there any user-facing changes?

No.

@github-actions github-actions bot added the datafusion Changes in the datafusion crate label Jan 21, 2022
@yjshen yjshen mentioned this pull request Jan 21, 2022
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yjshen commented Jan 21, 2022

Hi @alamb @tustvold could you please take a look?

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alamb approved these changes Jan 21, 2022
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Mechanically the changes in this PR make sense to me; Thanks @yjshen

@tustvold can you possibly take a look when you get a moment?

datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Show resolved Hide resolved
datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Outdated Show resolved Hide resolved
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I really like this change 👍

That being said I think it would be good to rename some things and update the corresponding comments to avoid future confusion. I also think it is possible to remove the Arc but I could be missing something...

datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Outdated Show resolved Hide resolved
datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Show resolved Hide resolved
datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Outdated Show resolved Hide resolved
datafusion/src/physical_plan/sorts/sort_preserving_merge.rs Outdated Show resolved Hide resolved
datafusion/src/physical_plan/sorts/mod.rs Show resolved Hide resolved
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yjshen commented Jan 22, 2022 •
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@alamb @tustvold Thanks for the review. I've updated the documentation, renamed variables, removed the record batch from SortKeyCursor, PTAL.

@yjshen yjshen requested a review from alamb January 22, 2022 02:11
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Looks like a great improvement to me 👍

@alamb alamb merged commit 62edddb into apache:master Jan 22, 2022
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alamb commented Jan 22, 2022

Thanks again @yjshen

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