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

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.0
• Fix Version/s: 2.3.0
• Component/s: SQL
• Assignee: L. C. Hsieh
• Reporter: Josh Rosen
• Created: 30/May/17 00:20
• Updated: 30/May/17 13:29
• Resolved: 30/May/17 13:29

Description

The following query parses in branch-2.2, but doesn't parse correctly as of today's master:

SELECT x FROM (SELECT 1 AS x)

It still parses if you name the subquery in the FROM clause:

SELECT x FROM (SELECT 1 AS x) t

In master, this gives the following error:

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)

== SQL ==
SELECT x FROM (SELECT 1 AS x)
---------^^^

  at org.apache.spark.sql.catalyst.parser.ParseException.withCommand(ParseDriver.scala:217)
  at org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parse(ParseDriver.scala:114)
  at org.apache.spark.sql.execution.SparkSqlParser.parse(SparkSqlParser.scala:48)
  at org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parsePlan(ParseDriver.scala:68)
  at org.apache.spark.sql.SparkSession.sql(SparkSession.scala:623)
  ... 48 elided

It looks like this change is intentional due to SPARK-20690, but the error message that we give here isn't very clear. I think that we should improve it so as not to confuse users.

Issue Links

• relates to: SPARK-20690 Subqueries in FROM should have alias names
• links to: [Github] Pull Request #18141 (viirya)