kosiew commented on code in PR #26382:
URL: https://github.com/apache/datafusion/pull/26382#discussion_r4492098902
##########
datafusion/sqllogictest/test_files/spark/math/pow.slt:
##########
@@ -142,19 +153,46 @@ SELECT pow(0.5, CAST('-Infinity' AS DOUBLE));
----
Infinity
+## A base of 1 or -1 with an infinite exponent gives NaN in Spark
+query R
+SELECT pow(1.0, CAST('Infinity' AS DOUBLE));
+----
+NaN
+
+query R
+SELECT pow(-1.0, CAST('Infinity' AS DOUBLE));
+----
+NaN
+
+query R
+SELECT pow(1.0, CAST('-Infinity' AS DOUBLE));
+----
+NaN
+
+query R
+SELECT pow(-1.0, CAST('-Infinity' AS DOUBLE));
+----
+NaN
+
# Test Array x Array
statement ok
CREATE TABLE t1(a DOUBLE, b DOUBLE) AS VALUES
(0.0, -1.0),
(2.0, 3.0),
-(CAST(NULL AS DOUBLE), 1.0);
+(CAST(NULL AS DOUBLE), 1.0),
+(CAST('-0.0' AS DOUBLE), -3.0),
+(1.0, CAST('NaN' AS DOUBLE)),
+(-1.0, CAST('Infinity' AS DOUBLE));
query R
SELECT pow(a, b) FROM t1;
Review Comment:
Optional coverage: could we add `SELECT pow(1.0, b), pow(a, CAST('Infinity'
AS DOUBLE)) FROM t1` before dropping the table? This would exercise
broadcasting in both argument positions and NULL-base propagation, though not
NULL-exponent propagation since `t1.b` contains no NULL. Both directions
already use the shared helper, so this is not a merge requirement.
##########
datafusion/spark/src/function/math/pow.rs:
##########
@@ -34,10 +35,12 @@ use datafusion_functions::math::power::PowerFunc;
/// Spark-compatible implementation of `pow` / `power`.
///
-/// Behavioural difference from the DataFusion default:
+/// Behavioural differences from the DataFusion default:
/// - `pow(0, <negative>)` → `Infinity` (IEEE 754 / Spark semantics)
/// The default raises `"zero raised to a negative power is undefined"` to
/// match PostgreSQL.
+/// - A `NaN` exponent, or a base of `1` or `-1` with an infinite exponent,
Review Comment:
Could we clarify the documentation to identify `pow(1, NaN)` as the
difference from default DataFusion, since `pow(2, NaN)` already returns NaN?
The zero-base description should also distinguish positive zero yielding
+Infinity from negative zero raised to a negative odd integer yielding
-Infinity.
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