stevomitric commented on code in PR #57680:
URL: https://github.com/apache/spark/pull/57680#discussion_r3749698588
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionHelper.scala:
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@@ -302,6 +302,35 @@ abstract class TypeCoercionHelper {
}
}
+ /** Whether `dt` is on the LTZ/NTZ timestamp fractional-precision axis (a
micro or nanos type). */
+ private def isTimestampFamily(dt: DataType): Boolean =
+ TimestampFamily.fractionalPrecision(dt).isDefined
+
+ /**
+ * Common operand type for [[SubtractTimestamps]] over two differing
timestamp-family operands.
+ * The operands are widened to the larger of the two fractional-second
precisions (the micro types
+ * count as 6, the nanos types carry their own precision `p` in [7, 9]) and
unified in one
+ * time-zone family:
+ * - a cross-family pair unifies in the no-time-zone (NTZ) family,
mirroring the microsecond
+ * precedent where TIMESTAMP - TIMESTAMP_NTZ coerces both operands to
TIMESTAMP_NTZ;
+ * - a same-family pair keeps that family, so a TIMESTAMP -
TIMESTAMP_LTZ(p) style pair still
+ * subtracts in the session time zone (DST-aware) exactly as a pure LTZ
pair does.
+ * The subtraction reads only each operand's epochMicros and always yields a
microsecond-grid
Review Comment:
Qualified both result types
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