perf: elide result null bitmap allocation for is-not-null scans - #788
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lizhen-0710 wants to merge 1 commit into
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perf: elide result null bitmap allocation for is-not-null scans#788lizhen-0710 wants to merge 1 commit into
lizhen-0710 wants to merge 1 commit into
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When a scan predicate is IS NOT NULL and the raw value is kept as the output type, the selected output cannot contain nulls. The previous path still prepared a result null bitmap for nullable input data, adding allocation pressure even though the bitmap was not needed by the final output. Teach SelectiveColumnReader to prepare output nulls through a guarded helper that skips result null bitmap allocation only for raw projected or extracted primitive, string, and binary outputs proven non-null by IS NOT NULL. Use the same helper from Parquet page reads so cross-page reads get the same behavior, and clear stale null state when output nulls are elided. Add common allocation tests and Parquet E2E coverage for compacted output, page and row-group paths, result reuse, scalar types, complex negative cases, filter-only columns, and mixed nullable outputs.
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What problem does this PR solve?
When a scan predicate is IS NOT NULL and the raw value is kept as the output type, selected output rows cannot contain nulls. The previous path could still prepare an internal result null bitmap whenever the input range had nulls. That bitmap was initialized and maintained by the reader, but was not attached to the final output vector.
Type of Change
Description
Teach SelectiveColumnReader to prepare output nulls through a guarded helper that skips result null bitmap allocation only for raw projected or extracted primitive, string, and binary outputs proven non-null by IS NOT NULL. Use the same helper from Parquet page reads so cross-page reads get the same behavior, and clear stale null state when output nulls are elided.
Add common allocation tests and Parquet E2E coverage for compacted output, page and row-group paths, result reuse, scalar types, complex negative cases, filter-only columns, and mixed nullable outputs.
Performance Impact
No Impact: This change does not affect the critical path (e.g., build system, doc, error handling).
Positive Impact: I have run benchmarks.
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Negative Impact: Explained below (e.g., trade-off for correctness).
Release Note
Please describe the changes in this PR
Release Note:
Checklist (For Author)
Breaking Changes
No
Yes (Description: ...)
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