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🟡 Changes recommended
Required, non-repeated columns still compress the unpopulated uncompressed_data_ buffer instead of the encoded values, producing invalid compressed V1 pages with mismatched declared uncompressed sizes.
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What changed in this PR
This PR reduces unnecessary buffer copying when the C++ Parquet writer builds data pages.
Changes:
- Reuses the values buffer for uncompressed V1 pages without definition or repetition levels.
- Removes an unused buffer copy when buffering dictionary-encoded V2 pages.
| File | Description |
|---|---|
cpp/src/parquet/column_writer.cc |
Avoids redundant copies in V1 and V2 data-page construction. |
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| // if dictionary encoding has fallen back to PLAIN | ||
| if (has_dictionary_ && !fallback_) { // Save pages until end of dictionary encoding | ||
| PARQUET_ASSIGN_OR_THROW(auto data_copy, | ||
| combined->CopySlice(0, combined->size(), allocator_)); |
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I checked the git history and suspect that the author of BuildDataPageV2 copied BuildDataPageV1 and modified it, failing to notice the unused variable. Meanwhile, clang-tidy didn't flag any warning here either.
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Rationale for this change
Avoid two unnecessary buffer copies.
What changes are included in this PR?
BuildDataPageV1uses thevaluesbuffer directly when there are no definition or repetition levels.BuildDataPageV2removes the unnecessarily copy ofcombinedwhen buffering dictionary-encoded pages.Are these changes tested?
Yes.
Are there any user-facing changes?
No.
Was AI used for this PR?
In accordance to the AI generation guidelines, please disclose below whether and how AI was used in this PR.
PR code and description written by:
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