allisonwang-db commented on a change in pull request #32303:
URL: https://github.com/apache/spark/pull/32303#discussion_r619415048
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File path: sql/core/src/test/resources/sql-tests/inputs/join-lateral.sql
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@@ -0,0 +1,84 @@
+-- Test cases for lateral join
+
+CREATE VIEW t1(c1, c2) AS VALUES (0, 1), (1, 2);
+CREATE VIEW t2(c1, c2) AS VALUES (0, 2), (0, 3);
+
+-- lateral join with single column select
+SELECT * FROM t1, LATERAL (SELECT c1);
Review comment:
> Is this compiled into a join query? We cannot compile it into a simple
scan query like PostgreSQL?
>
> ```
> postgres=# explain SELECT * FROM t1, LATERAL (SELECT c1) t2;
> QUERY PLAN
> --------------------------------------------------------------
> Values Scan on "*VALUES*" (cost=0.00..0.03 rows=2 width=12)
> (1 row)
> ```
Yes it should be rewritten as a simple scan query`SELECT c1 FROM t1` instead
of a join query. I am thinking about adding an optimizer rule for
OneRowRelation. This can be applied to correlated subqueries as well.
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