DRAFT: [C++][Parquet] Use num_nulls from DataPageV2 to skip null handling

[pitrou]

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

In the case of PARQUET issues on JIRA the title also supports:

PARQUET-${JIRA_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[pitrou]

@ursabot please benchmark

[ursabot]

Benchmark runs are scheduled for commit c13fe56. Watch https://buildkite.com/apache-arrow and https://conbench.ursa.dev for updates. A comment will be posted here when the runs are complete.

[pitrou]

@mapleFU I came up with this simple optimization. I'm not sure it will make a difference in practice...

[mapleFU]

maybe a better name or comment for nulls_ ? Since max_rep_level_ > 0 and null is weird

[mapleFU]

I didn't go through this carefully, and I think generally this is ok, for page-v1 it's also ok when num_nulls in stats exists and equal to 0?

(Besides, personally we're using column-index to predict. and in parquet community page-v2 is not enabled by default 🤔 Maybe I should pick up the filtering patch ( #39731 ) after my vocation this month... )

[conbench-apache-arrow]

Thanks for your patience. Conbench analyzed the 4 benchmarking runs that have been run so far on PR commit c13fe56.

There were 16 benchmark results indicating a performance regression:

• Pull Request Run on amd64-c6a-4xlarge-linux at 2024-09-04 18:01:23Z
  • BenchmarkTemporalRounding (C++) with params=<FloorTemporal, zoned, round_10_week>/524288/0, source=cpp-micro, suite=arrow-compute-scalar-temporal-benchmark
  • ErrorSchemeBool (C++) with source=cpp-micro, suite=arrow-type-benchmark
• and 14 more (see the report linked below)

The full Conbench report has more details.

[mapleFU]

I've checked FLBARecordReader, it's ReadDense uses a extra null_bitmap_builder_, sigh

[mapleFU]

After read this part of code this idea lgtm

[github-actions]

Thank you for your contribution. Unfortunately, this pull request has been marked as stale because it has had no activity in the past 365 days. Please remove the stale label or comment below, or this PR will be closed in 14 days. Feel free to re-open this if it has been closed in error. If you do not have repository permissions to reopen the PR, please tag a maintainer.