[SPARK-17982][SQL][BACKPORT-2.0] SQLBuilder should wrap the generated SQL with parenthesis for LIMIT

[dongjoon-hyun]

What changes were proposed in this pull request?

Currently, SQLBuilder handles LIMIT by always adding LIMIT at the end of the generated subSQL. It makes RuntimeExceptions like the following. This PR adds a parenthesis always except SubqueryAlias is used together with LIMIT.

Before

scala> sql("CREATE TABLE tbl(id INT)")
scala> sql("CREATE VIEW v1(id2) AS SELECT id FROM tbl LIMIT 2")
java.lang.RuntimeException: Failed to analyze the canonicalized SQL: ...

After

scala> sql("CREATE TABLE tbl(id INT)")
scala> sql("CREATE VIEW v1(id2) AS SELECT id FROM tbl LIMIT 2")
scala> sql("SELECT id2 FROM v1")
res4: org.apache.spark.sql.DataFrame = [id2: int]

Fixed cases in this PR

The following two cases are the detail query plans having problematic SQL generations.

1. SELECT * FROM (SELECT id FROM tbl LIMIT 2)

   Please note that FROM SELECT part of the generated SQL in the below. When we don't use '()' for limit, this fails.

# Original logical plan:
Project [id#1]
+- GlobalLimit 2
   +- LocalLimit 2
      +- Project [id#1]
         +- MetastoreRelation default, tbl

# Canonicalized logical plan:
Project [gen_attr_0#1 AS id#4]
+- SubqueryAlias tbl
   +- Project [gen_attr_0#1]
      +- GlobalLimit 2
         +- LocalLimit 2
            +- Project [gen_attr_0#1]
               +- SubqueryAlias gen_subquery_0
                  +- Project [id#1 AS gen_attr_0#1]
                     +- SQLTable default, tbl, [id#1]

# Generated SQL:
SELECT `gen_attr_0` AS `id` FROM (SELECT `gen_attr_0` FROM SELECT `gen_attr_0` FROM (SELECT `id` AS `gen_attr_0` FROM `default`.`tbl`) AS gen_subquery_0 LIMIT 2) AS tbl

2. SELECT * FROM (SELECT id FROM tbl TABLESAMPLE (2 ROWS))

   Please note that ((~~~) AS gen_subquery_0 LIMIT 2) in the below. When we use '()' for limit on SubqueryAlias, this fails.

# Original logical plan:
Project [id#1]
+- Project [id#1]
   +- GlobalLimit 2
      +- LocalLimit 2
         +- MetastoreRelation default, tbl

# Canonicalized logical plan:
Project [gen_attr_0#1 AS id#4]
+- SubqueryAlias tbl
   +- Project [gen_attr_0#1]
      +- GlobalLimit 2
         +- LocalLimit 2
            +- SubqueryAlias gen_subquery_0
               +- Project [id#1 AS gen_attr_0#1]
                  +- SQLTable default, tbl, [id#1]

# Generated SQL:
SELECT `gen_attr_0` AS `id` FROM (SELECT `gen_attr_0` FROM ((SELECT `id` AS `gen_attr_0` FROM `default`.`tbl`) AS gen_subquery_0 LIMIT 2)) AS tbl

How was this patch tested?

Pass the Jenkins test with a newly added test case.

[dongjoon-hyun]

Hi, @gatorsmile .
This is a backport of #15546 for branch-2.0.

[gatorsmile]

LGTM pending jenkins

[dongjoon-hyun]

Thank you again, @gatorsmile !

[SparkQA]

Test build #68542 has finished for PR 15856 at commit 92d901b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

@dongjoon-hyun Thanks! It has been merged. Could you close it?

[dongjoon-hyun]

Thank you!