shangxinli commented on code in PR #20458:
URL: https://github.com/apache/hudi/pull/20458#discussion_r4433899802
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hudi-spark-datasource/hudi-spark-common/src/main/scala/org/apache/spark/sql/HoodieSparkTypeUtils.scala:
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@@ -36,9 +36,18 @@ object HoodieSparkTypeUtils {
def isCastPreservingOrdering(from: DataType, to: DataType): Boolean =
(from, to) match {
// NOTE: In the casting rules defined by Spark, only casting from String
to Numeric
- // (and vice versa) are the only casts that might break the ordering of
the elements after casting
- case (StringType, _: NumericType) => false
- case (_: NumericType, StringType) => false
+ // (and vice versa) are the only casts that might break the ordering of
the elements after casting.
+ // These match by type, so that collated strings on Spark 4 are rejected
as well
+ case (_: StringType, _: NumericType) => false
+ case (_: NumericType, _: StringType) => false
+ // NOTE: On Spark 4 StringType carries a collation, and casting to a
different collation changes
+ // the sort order (for ex, "B" < "a" in UTF8_BINARY but "a" < "B"
in UTF8_LCASE). Equality
+ // also compares the char/varchar length constraint, so those
casts are conservatively
+ // rejected too. On Spark 3 StringType is a singleton, making this
arm trivially true
+ case (fromStr: StringType, toStr: StringType) => fromStr == toStr
+ // NOTE: Every type casts to a string, so collated targets are rejected
whatever the source
+ // (for ex, binary bounds are in byte order, which UTF8_LCASE does
not follow)
+ case (_, toStr: StringType) => toStr == StringType
case _ => true
Review Comment:
This still falls through to true for a collated StringType cast to a
non-string type, like BinaryType -- binary bounds are byte-ordered, which
UTF8_LCASE doesn't follow.
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