[fix](simplify agg) SimplifyAggGroupBy should verify injectivity#64335
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yujun777 wants to merge 1 commit into
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[fix](simplify agg) SimplifyAggGroupBy should verify injectivity#64335yujun777 wants to merge 1 commit into
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The rule simplified GROUP BY f(x) to GROUP BY x without verifying that f(x) is injective (one-to-one). This caused wrong results when: - literal is NULL (any op: a+NULL → always NULL) - Multiply/Divide by zero (a*0 → always 0) - Multiply/Divide with float/double operands (precision loss) Also adds proper handling of implicit lossless widening casts (integral→integral, float→double, integral→decimal, decimal→decimal) and removes the now-unused ExpressionUtils.extractSlotOrCastOnSlot. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
yujun777
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924060929,
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morrySnow and
starocean999
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run buildall |
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run buildall |
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TPC-H: Total hot run time: 29419 ms |
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TPC-DS: Total hot run time: 169732 ms |
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TPC-H: Total hot run time: 28739 ms |
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TPC-DS: Total hot run time: 169104 ms |
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morrySnow
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Jun 10, 2026
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| protected static boolean isLosslessWidening(DataType src, DataType tgt) { |
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in #64080, DataType add a new interface isInjectiveCastTo, i think we could reuse it here
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Problem
SimplifyAggGroupBysimplifiedGROUP BY f(x)toGROUP BY xwithoutverifying that
f(x)is injective (one-to-one). This caused wrong results:a * 0/0 * a0 / aa / 0a + NULL/a * NULL/ ...a * 0.1with float/doubleFix
isBinaryArithmeticSlot: restructured to separate slot-expr from literal,then validate each independently. Float/double check runs early, before
slot extraction.
New
checkLiteral(expr, literal): rejects NULL literal andMultiply/Divide by zero.
New
canExtractSlot(expr): replaces the old unconditionalextractSlotOrCastOnSlot— only accepts bareSlotor implicit losslesswidening casts (integral→integral, float→double, integral→decimal,
decimal→decimal). Range and scale are compared directly for correctness.
New
isLosslessWidening(src, tgt): type-family-aware widening checkusing
width()for integral/float, andDecimalV3Type.forType()fordecimal range/scale comparison.
Changes
SimplifyAggGroupBy.java: +80 lines, rewritten core logicExpressionUtils.java: -35 lines, removed unusedisSlotOrCastOnSlot/extractSlotOrCastOnSlotSimplifyAggGroupByTest.java: +216 lines, 25 tests covering all new paths