uros-b commented on code in PR #57680:
URL: https://github.com/apache/spark/pull/57680#discussion_r3700469336
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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
+ * DayTimeIntervalType, so widening the precision never changes the numeric
result -- it only
+ * keeps the two operands the same concrete type. For a pure-micro
cross-family pair this returns
+ * TimestampNTZType, identical to the pre-nanos behavior.
+ */
+ private def subtractTimestampsCommonType(dt1: DataType, dt2: DataType):
DataType = {
+ val p = math.max(
+ TimestampFamily.fractionalPrecision(dt1).getOrElse(6),
+ TimestampFamily.fractionalPrecision(dt2).getOrElse(6))
+ if (TimestampFamily.isLtz(dt1) && TimestampFamily.isLtz(dt2)) {
+ if (p <= 6) TimestampType else TimestampLTZNanosType(p)
+ } else {
+ if (p <= 6) TimestampNTZType else TimestampNTZNanosType(p)
Review Comment:
Nearby findWiderDateTimeType uses MicrosPrecision = 6;
subtractTimestampsCommonType hardcodes 6. Prefer the same named constant for
consistency.
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