[branch-54] Fix TopK DISTINCT aggregation preserving NULLs (#22571)#22634
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alamb wants to merge 1 commit into
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[branch-54] Fix TopK DISTINCT aggregation preserving NULLs (#22571)#22634alamb wants to merge 1 commit into
alamb wants to merge 1 commit into
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## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123. --> - Closes #22554. ## Rationale for this change TopK aggregation dropped NULL group keys for ordered DISTINCT queries. For example, `SELECT DISTINCT v FROM t ORDER BY v ASC NULLS FIRST LIMIT 1` could return an empty string instead of NULL when TopK aggregation was enabled. <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> ## What changes are included in this PR? This PR preserves NULL group keys for DISTINCT TopK aggregation by tracking whether a NULL group key was seen separately from the heap. The heap still only stores non-NULL values. This avoids making the TopK heap implementations handle NULL values directly. The stream also now marks itself done after emitting, so NULL-only DISTINCT results are emitted once and do not repeat. <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> ## Are these changes tested? Yes <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> ## Are there any user-facing changes? No API Change <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. -->
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54.0.0(Apr 2026 / May 2026) #21080This PR:
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