[SPARK-27922][SQL][PYTHON][TESTS] Convert and port 'natural-join.sql' into UDF test base

sql/core/src/test/resources/sql-tests/inputs/udf/udf-natural-join.sql

@@ -0,0 +1,29 @@
+-- List of configuration the test suite is run against:
+--SET spark.sql.autoBroadcastJoinThreshold=10485760
+--SET spark.sql.autoBroadcastJoinThreshold=-1,spark.sql.join.preferSortMergeJoin=true
+--SET spark.sql.autoBroadcastJoinThreshold=-1,spark.sql.join.preferSortMergeJoin=false
+
+-- This test file was converted from natural-join.sql.
+-- Note that currently registered UDF returns a string. So there are some differences, for instance
+-- in string cast within UDF in Scala and Python.
+
+create temporary view nt1 as select * from values
+  ("one", 1),
+  ("two", 2),
+  ("three", 3)
+  as nt1(k, v1);
+
+create temporary view nt2 as select * from values
+  ("one", 1),
+  ("two", 22),
+  ("one", 5)
+  as nt2(k, v2);
+
+
+SELECT * FROM nt1 natural join nt2 where udf(k) = "one";
+
+SELECT * FROM nt1 natural left join nt2 where k <> udf("") order by v1, v2;
+
+SELECT * FROM nt1 natural right join nt2 where udf(k) <> udf("") order by v1, v2;
+
+SELECT udf(count(*)) FROM nt1 natural full outer join nt2;

sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out

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+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 6
+
+
+-- !query 0
+create temporary view nt1 as select * from values
+  ("one", 1),
+  ("two", 2),
+  ("three", 3)
+  as nt1(k, v1)
+-- !query 0 schema
+struct<>
+-- !query 0 output
+
+
+
+-- !query 1
+create temporary view nt2 as select * from values
+  ("one", 1),
+  ("two", 22),
+  ("one", 5)
+  as nt2(k, v2)
+-- !query 1 schema
+struct<>
+-- !query 1 output
+
+
+
+-- !query 2
+SELECT * FROM nt1 natural join nt2 where udf(k) = "one"
+-- !query 2 schema
+struct<k:string,v1:int,v2:int>
+-- !query 2 output
+one	1	1
+one	1	5
+
+
+-- !query 3
+SELECT * FROM nt1 natural left join nt2 where k <> udf("") order by v1, v2
+-- !query 3 schema
+struct<k:string,v1:int,v2:int>
+-- !query 3 output
+one	1	1
+one	1	5
+two	2	22
+three	3	NULL
+
+
+-- !query 4
+SELECT * FROM nt1 natural right join nt2 where udf(k) <> udf("") order by v1, v2
+-- !query 4 schema
+struct<k:string,v1:int,v2:int>
+-- !query 4 output
+one	1	1
+one	1	5
+two	2	22
+
+
+-- !query 5
+SELECT udf(count(*)) FROM nt1 natural full outer join nt2
+-- !query 5 schema
+struct<udf(count(1)):string>
+-- !query 5 output
+4