Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/18460#discussion_r143238804
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -100,6 +101,17 @@ object TypeCoercion {
case (_: TimestampType, _: DateType) | (_: DateType, _: TimestampType)
=>
Some(TimestampType)
+ case (t1 @ StructType(fields1), t2 @ StructType(fields2)) if
t1.sameType(t2) =>
+ Some(StructType(fields1.zip(fields2).map { case (f1, f2) =>
+ // Since `t1.sameType(t2)` is true, two StructTypes have the same
DataType
+ // except `name` (in case of `spark.sql.caseSensitive=false`) and
`nullable`.
+ // - Different names: use a lower case name because
findTightestCommonType is commutative.
+ // - Different nullabilities: `nullable` is true iff one of them
is nullable.
+ val name = if (f1.name == f2.name) f1.name else
f1.name.toLowerCase(Locale.ROOT)
--- End diff --
Why the output nested column name is lower case? Is Hive behaving like this?
In addition, could you add one more test and check whether we also respect
case sensitivity conf when we resolve the queries that contain the nested
column in the references?
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