wombatu-kun commented on code in PR #20458:
URL: https://github.com/apache/hudi/pull/20458#discussion_r4408081760
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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 +36,15 @@ 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
Review Comment:
A binary column cast directly to a collated string (`CAST(bin AS STRING
COLLATE UTF8_LCASE) = 'a'`) still falls through to `case _ => true`, and column
stats V2 indexes binary columns, so its byte-ordered bounds get compared in
UTF8_LCASE just like in the repro. Should `(BinaryType, toStr: StringType)`
also be rejected unless `toStr == StringType`?
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