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…olumn A nullable UNIQUE column permits multiple NULL rows that may differ in other columns, so it does not functionally determine them once NULLs are grouped together. Only use dependencies that are valid across NULLs when removing redundant GROUP BY expressions.
Only eliminate DISTINCT when the functional dependency remains valid across NULLs, preventing duplicate NULL values after GROUP BY. Add SQL regressions for grouped projections, aliases, subqueries, outer counts, and composite keys. Preserve NOT NULL UNIQUE optimizations.
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Additional details and impacted files@@ Coverage Diff @@
## main #26220 +/- ##
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- Coverage 82.93% 82.93% -0.01%
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Files 1154 1154
Lines 458002 458049 +47
Branches 458002 458049 +47
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jayzhan211
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Oct 23, 2026
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Thanks @buraksenn , LGTM
jayzhan211
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October 23, 2026 07:42
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Which issue does this PR close?
Rationale for this change
A nullable UNIQUE column permits multiple NULL rows, so it cannot safely
determine other grouping columns. Dropping those columns can merge distinct
groups and return incorrect results.
What changes are included in this PR?
What is the testing strategy for this PR?
SLT and plan-builder tests cover nullable and composite UNIQUE keys,
DISTINCT after GROUP BY, and valid PRIMARY KEY / NOT NULL UNIQUE cases.
The DISTINCT regressions fail without the fix.
Are there any user-facing changes?
Yes: incorrect results are fixed