Github user liutang123 commented on a diff in the pull request:
https://github.com/apache/spark/pull/21100#discussion_r183005177
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
---
@@ -896,6 +896,19 @@ class SQLQuerySuite extends QueryTest with
SharedSQLContext {
}
}
+ test("SPARK-24012 Union of map and other compatible columns") {
+ checkAnswer(
+ sql(
+ """
+ |SELECT map(1, 2), 'str'
+ |UNION ALL
+ |SELECT map(1, 2, 3, NULL), 1""".stripMargin),
--- End diff --
Of course we can.
two solutionï¼
1. Try cast two map types to one no matter key types are not the same or
value types are not the same.
`select map(1, 2) union all map(1, 'str')` will work.
2. Cast two map type to one only when the key type and value type are the
same. This solution just resolve the problem that map<t1, nullable t2> and
map<t1, not nullable t2> can't be union.
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