Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/17174#discussion_r105097503
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -324,14 +324,22 @@ object TypeCoercion {
// We should cast all relative timestamp/date/string comparison into
string comparisons
// This behaves as a user would expect because timestamp strings
sort lexicographically.
// i.e. TimeStamp(2013-01-01 00:00 ...) < "2014" = true
- case p @ BinaryComparison(left @ StringType(), right @ DateType()) =>
- p.makeCopy(Array(left, Cast(right, StringType)))
- case p @ BinaryComparison(left @ DateType(), right @ StringType()) =>
- p.makeCopy(Array(Cast(left, StringType), right))
- case p @ BinaryComparison(left @ StringType(), right @
TimestampType()) =>
- p.makeCopy(Array(left, Cast(right, StringType)))
- case p @ BinaryComparison(left @ TimestampType(), right @
StringType()) =>
- p.makeCopy(Array(Cast(left, StringType), right))
+ // If StringType is foldable then we need to cast String to Date or
Timestamp type
+ // which would give order of magnitude performance gain as well as
preserve the behavior
+ // achieved by expressed above
+ // TimeStamp(2013-01-01 00:00 ...) < Cast( "2014" as timestamp) =
true
+ case p @ BinaryComparison(left @ StringType(), right) if
dateOrTimestampType(right) =>
+ if (left.foldable) {
+ p.makeCopy(Array(Cast(left, right.dataType), right))
--- End diff --
Without this change, I think you can still explicitly cast the string to
time/date in order to speed up the comparison, right?
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