[SPARK-24012][SQL] Union of map and other compatible column

## What changes were proposed in this pull request?
Union of map and other compatible column result in unresolved operator 'Union; exception

Reproduction
`spark-sql>select map(1,2), 'str' union all select map(1,2,3,null), 1`
Output:
```
Error in query: unresolved operator 'Union;;
'Union
:- Project [map(1, 2) AS map(1, 2)#106, str AS str#107]
:  +- OneRowRelation$
+- Project [map(1, cast(2 as int), 3, cast(null as int)) AS map(1, CAST(2 AS INT), 3, CAST(NULL AS INT))#109, 1 AS 1#108]
   +- OneRowRelation$
```
So, we should cast part of columns to be compatible when appropriate.

## How was this patch tested?
Added a test (query union of map and other columns) to SQLQueryTestSuite's union.sql.

Author: liutang123 <[email protected]>

Closes apache#21100 from liutang123/SPARK-24012.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala

@@ -112,6 +112,14 @@ object TypeCoercion {
         StructField(f1.name, dataType, nullable = f1.nullable || f2.nullable)
       }))
 
+    case (a1 @ ArrayType(et1, hasNull1), a2 @ ArrayType(et2, hasNull2)) if a1.sameType(a2) =>
+      findTightestCommonType(et1, et2).map(ArrayType(_, hasNull1 || hasNull2))
+
+    case (m1 @ MapType(kt1, vt1, hasNull1), m2 @ MapType(kt2, vt2, hasNull2)) if m1.sameType(m2) =>
+      val keyType = findTightestCommonType(kt1, kt2)
+      val valueType = findTightestCommonType(vt1, vt2)
+      Some(MapType(keyType.get, valueType.get, hasNull1 || hasNull2))
+
     case _ => None
   }
 

sql/core/src/test/resources/sql-tests/inputs/union.sql

@@ -35,6 +35,17 @@ FROM   (SELECT col AS col
               SELECT col
               FROM p3) T1) T2;
 
+-- SPARK-24012 Union of map and other compatible columns.
+SELECT map(1, 2), 'str'
+UNION ALL
+SELECT map(1, 2, 3, NULL), 1;
+
+-- SPARK-24012 Union of array and other compatible columns.
+SELECT array(1, 2), 'str'
+UNION ALL
+SELECT array(1, 2, 3, NULL), 1;
+
+
 -- Clean-up
 DROP VIEW IF EXISTS t1;
 DROP VIEW IF EXISTS t2;

sql/core/src/test/resources/sql-tests/results/union.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 14
+-- Number of queries: 16
 
 
 -- !query 0
@@ -105,40 +105,62 @@ struct<x:int,col:int>
 
 
 -- !query 9
-DROP VIEW IF EXISTS t1
+SELECT map(1, 2), 'str'
+UNION ALL
+SELECT map(1, 2, 3, NULL), 1
 -- !query 9 schema
-struct<>
+struct<map(1, 2):map<int,int>,str:string>
 -- !query 9 output
-
+{1:2,3:null}	1
+{1:2}	str
 
 
 -- !query 10
-DROP VIEW IF EXISTS t2
+SELECT array(1, 2), 'str'
+UNION ALL
+SELECT array(1, 2, 3, NULL), 1
 -- !query 10 schema
-struct<>
+struct<array(1, 2):array<int>,str:string>
 -- !query 10 output
-
+[1,2,3,null]	1
+[1,2]	str
 
 
 -- !query 11
-DROP VIEW IF EXISTS p1
+DROP VIEW IF EXISTS t1
 -- !query 11 schema
 struct<>
 -- !query 11 output
 
 
 
 -- !query 12
-DROP VIEW IF EXISTS p2
+DROP VIEW IF EXISTS t2
 -- !query 12 schema
 struct<>
 -- !query 12 output
 
 
 
 -- !query 13
-DROP VIEW IF EXISTS p3
+DROP VIEW IF EXISTS p1
 -- !query 13 schema
 struct<>
 -- !query 13 output
 
+
+
+-- !query 14
+DROP VIEW IF EXISTS p2
+-- !query 14 schema
+struct<>
+-- !query 14 output
+
+
+
+-- !query 15
+DROP VIEW IF EXISTS p3
+-- !query 15 schema
+struct<>
+-- !query 15 output
+