cloud-fan commented on code in PR #44480:
URL: https://github.com/apache/spark/pull/44480#discussion_r1436440200
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/UnwrapCastInBinaryComparison.scala:
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@@ -144,6 +144,15 @@ object UnwrapCastInBinaryComparison extends
Rule[LogicalPlan] {
value != null =>
Some(unwrapTimestampToDate(be, fromExp, ts, timeZoneId, evalMode))
+ // Timestamp/Timestamp_NTZ -> Timestamp_NTZ/Timestamp
Review Comment:
`cast(ts_ntz_col as ts) compare ts_lit` means `convertTz(col_value, tz, UTC)
compare lit_value`, and we are trying to reverse it to `col_value compare
convertTz(lit_value, UTC, tz)`.
We need to be careful here, as datetime with timezone is very tricky. My
proposal is to do a round trip tests before rewriting it: if
`convertTz(convertTz(lit_value, UTC, tz), tz, UTC) == lit_value`. This means we
convert the comparison to `convertTz(col_value, tz, UTC) compare
convertTz(convertTz(lit_value, UTC, tz), tz, UTC) == lit_value` first, and we
strip the `convertTz(_, tz, UTC)` from both sides.
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