[SPARK-20916][SQL] Improve error message for unaliased subqueries in FROM clause

[viirya]

What changes were proposed in this pull request?

We changed the parser to reject unaliased subqueries in the FROM clause in SPARK-20690. However, the error message that we now give isn't very helpful:

scala> sql("""SELECT x FROM (SELECT 1 AS x)""")
org.apache.spark.sql.catalyst.parser.ParseException:
mismatched input 'FROM' expecting {<EOF>, 'WHERE', 'GROUP', 'ORDER', 'HAVING', 'LIMIT', 'LATERAL', 'WINDOW', 'UNION', 'EXCEPT', 'MINUS', 'INTERSECT', 'SORT', 'CLUSTER', 'DISTRIBUTE'}(line 1, pos 9)

We should modify the parser to throw a more clear error for such queries:

scala> sql("""SELECT x FROM (SELECT 1 AS x)""")
org.apache.spark.sql.catalyst.parser.ParseException:
The unaliased subqueries in the FROM clause are not supported.(line 1, pos 14)

How was this patch tested?

Modified existing tests to reflect this change.

[viirya]

cc @JoshRosen @cloud-fan @hvanhovell @gatorsmile

[maropu]

Better to add tests in SQLQueryTestSuite?

[viirya]

@maropu Sure. Thanks.

[SparkQA]

Test build #77521 has started for PR 18141 at commit f64df52.

[SparkQA]

Test build #77517 has finished for PR 18141 at commit 0a7eab0.

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

[gatorsmile]

Could you move the test case sql-tests/inputs/aliased-subquery-in-from.sql to sql-tests/inputs/subquery/subquery-in-from.sql?

[viirya]

Sure.

[gatorsmile]

LGTM except one comment

[SparkQA]

Test build #77524 has started for PR 18141 at commit 7135bbc.

[viirya]

retest this please.

[SparkQA]

Test build #77525 has finished for PR 18141 at commit 7135bbc.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #77528 has finished for PR 18141 at commit cc7c572.

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

[cloud-fan]

LGTM, merging to master!