branch-4.1: [fix](simplify agg) SimplifyAggGroupBy should verify injectivity #64335#65109
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) ## Problem `SimplifyAggGroupBy` simplified `GROUP BY f(x)` to `GROUP BY x` without verifying that `f(x)` is injective (one-to-one). This caused wrong results: | Expression | Why wrong | |---|---| | `a * 0` / `0 * a` | always evaluates to 0 — all rows fall into one group | | `0 / a` | always evaluates to 0 | | `a / 0` | division by zero | | `a + NULL` / `a * NULL` / ... | always evaluates to NULL | | `a * 0.1` with float/double | precision loss may map different inputs to same result | ## Fix 1. **`isBinaryArithmeticSlot`**: restructured to separate slot-expr from literal, then validate each independently. Float/double check runs early, before slot extraction. 2. **New `checkLiteral(expr, literal)`**: rejects NULL literal and Multiply/Divide by zero. 3. **New `canExtractSlot(expr)`**: replaces the old unconditional `extractSlotOrCastOnSlot` — only accepts bare `Slot` or implicit lossless widening casts (integral→integral, float→double, integral→decimal, decimal→decimal). Range and scale are compared directly for correctness. ## Changes - `SimplifyAggGroupBy.java`: +80 lines, rewritten core logic - `ExpressionUtils.java`: -35 lines, removed unused `isSlotOrCastOnSlot` / `extractSlotOrCastOnSlot` - `SimplifyAggGroupByTest.java`: +216 lines, 25 tests covering all new paths --------- Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
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yiguolei
approved these changes
Jul 2, 2026
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Cherry-picked from #64335