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GH-50778: [C++][Parquet] Fix chunked level histogram accumulation - #50780

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pitrou merged 1 commit into
apache:mainfrom
wecharyu:fix_update_level_hist
Aug 31, 2026
Merged

pitrou merged 1 commit into
apache:mainfrom
wecharyu:fix_update_level_hist

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@wecharyu

@wecharyu wecharyu commented Aug 3, 2026 •

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Rationale for this change

UpdateLevelHistogram incorrectly accumulated from the beginning of the input on every iteration of its max_level == 1 fast path. Inputs spanning multiple chunks therefore counted the first chunk repeatedly.

Fix #50778.

What changes are included in this PR?

  • Accumulate the current chunk using it rather than levels.begin().
  • Add a UT

Are these changes tested?

Yes, passing the new UT and existing UT.

Are there any user-facing changes?

No.

@github-actions

github-actions Bot commented Aug 3, 2026

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⚠️ GitHub issue #50778 has been automatically assigned in GitHub to PR creator.

@wgtmac wgtmac left a comment

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Good catch! Thanks @wecharyu!

@wecharyu

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@wgtmac Can we merge this if no more concerns? Thanks!

@pitrou pitrou changed the title GH-50778: [C++] Fix chunked level histogram accumulation GH-50778: [C++][Parquet] Fix chunked level histogram accumulation Aug 31, 2026
@pitrou
pitrou merged commit 95beeb2 into apache:main Aug 31, 2026
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[C++] UpdateLevelHistogram produces incorrect histograms in fast path

3 participants