fix: avoid dividing by zero in avg for decimals with a negative scale - #24899
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edubraqd wants to merge 1 commit into
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fix: avoid dividing by zero in avg for decimals with a negative scale#24899edubraqd wants to merge 1 commit into
avg for decimals with a negative scale#24899edubraqd wants to merge 1 commit into
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`DecimalAverager::try_new` computed `10^sum_scale` and `10^target_scale`
separately with `pow_wrapping(scale as u32)`. For a negative scale the
exponent wraps to a huge value and the result is 0, so `avg` later divided
by zero:
SELECT avg(x) FROM (VALUES (arrow_cast(1, 'Decimal128(10, -2)'))) t(x);
thread 'main' panicked ... attempt to divide by zero
The two factors were only ever used as the ratio `10^(target_scale -
sum_scale)`, so compute that directly from the scale difference. The
existing "Arithmetic Overflow in AvgAccumulator" error for a target scale
smaller than the sum scale is kept.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Which issue does this PR close?
avgover a decimal with a negative scale panics with "attempt to divide by zero" #24898.Rationale for this change
DecimalAverager::try_newcomputed10^sum_scaleand10^target_scaleseparately withpow_wrapping(scale as u32). For a negative scale the exponent wraps and the result is 0, soavgdivided by zero and panicked for any decimal input with a negative scale.What changes are included in this PR?
The two factors were only ever used as the ratio
10^(target_scale - sum_scale), soDecimalAveragernow stores that single multiplier, computed from the scale difference. The existingArithmetic Overflow in AvgAccumulatorerror for a target scale smaller than the sum scale is kept (it is now thescale_diff < 0check).Are these changes tested?
Yes.
avg_decimal_negative_scaleaveragesDecimal128(10, -2)values and checks theDecimal128(14, 2)result; it used to panic. The existingaverageandfunctions-aggregate-commonunit tests pass.Are there any user-facing changes?
avgover decimals with a negative scale returns a result instead of panicking.