Feat: Allow pow with negative & non-integer exponent on decimals (#19…#90
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gh-worker-dd-mergequeue-cf854d[bot] merged 1 commit intoDataDog:branch-52from Mar 4, 2026
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…che#19369) ## Which issue does this PR close? Closes apache#19348 ## Rationale for this change Previously, pow() on decimal types would error for negative exponents and non-integer exponents with messages like: - Arrow error: Arithmetic overflow: Unsupported exp value: -5 - Compute error: Cannot use non-integer exp - This was a regression from when decimals were cast to float before pow(). The efficient integer-based algorithm for computing power on scaled integers cannot handle these cases. ## What changes are included in this PR? - Modified pow_decimal_int to fallback to pow_decimal_float for negative exponents - Modified pow_decimal_float to use an efficient integer path for non-negative integer exponents, otherwise fallback to f64 computation Added pow_decimal_float_fallback function that: - Converts the decimal to f64 - Computes powf(exp) - Converts back to the original decimal type with proper scaling - Added decimal_from_i128 helper to convert i128 results back to generic decimal types (needed for Decimal256 support) - Updated sqllogictests to expect success for negative/non-integer exponents ## Are these changes tested? Yes: Unit tests for pow_decimal_float_fallback covering negative exponents, fractional exponents, cube roots Updated SQL logic tests in decimal.slt ## Are there any user-facing changes? Yes. The following queries now work instead of returning errors: ```sql -- Negative exponent SELECT power(4::decimal(38, 5), -1); -- Returns 0.25 -- Non-integer exponent SELECT power(2.5, 4.2); -- Returns 46.9 -- Square root via power SELECT power(4::decimal, 0.5); -- Returns 2 (cherry picked from commit 1d5d63c)
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Add a commit from upstream to allow negative exponents