Github user mgaido91 commented on a diff in the pull request:
https://github.com/apache/spark/pull/21620#discussion_r197726949
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -536,6 +536,11 @@ object TypeCoercion {
case None => c
}
+ case ArrayJoin(arr, d, nr) if
!ArrayType(StringType).acceptsType(arr.dataType) &&
+ ArrayType.acceptsType(arr.dataType) =>
+ val containsNull =
arr.dataType.asInstanceOf[ArrayType].containsNull
+ ArrayJoin(Cast(arr, ArrayType(StringType, containsNull)), d, nr)
--- End diff --
I am not sure. I think it is arguable which is the right result of `SELECT
array_join(array(array('a', 'b'), array('c', 'd')), ';')` for instance. With
this PR, the result is `[a, b];[c, d]` but shouldn't it be `[a;b];[c;d]`?
Moreover, Presto, which is the reference here, doesn't support nested arrays
for instance:
```
presto> select array_join(array[array[1, 2, 3], array[3, 4, 5]], ';');
Query 20180625_090549_00003_bsbcg failed: Input type array(integer) not
supported
```
So, I'd avoid that.
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