[jira] [Commented] (SPARK-17114) Adding a 'GROUP BY 1' where first column is literal results in wrong answer

["Josh Rosen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-17114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15425445#comment-15425445 ] 

Josh Rosen commented on SPARK-17114:
------------------------------------

Even if we decide that Spark's current interpretation of this query is correct, we should add a test case to make sure that it doesn't change.

I'd be curious to see whether the ANSI SQL standards say anything about the interpretation of this weird corner-case query.

> Adding a 'GROUP BY 1' where first column is literal results in wrong answer
> ---------------------------------------------------------------------------
>
>                 Key: SPARK-17114
>                 URL: https://issues.apache.org/jira/browse/SPARK-17114
>             Project: Spark
>          Issue Type: Bug
>    Affects Versions: 1.6.2, 2.0.0
>            Reporter: Josh Rosen
>
> Consider the following example:
> {code}
> sc.parallelize(Seq(128, 256)).toDF("int_col").registerTempTable("mytable")
> // The following query should return an empty result set because the `IN` filter condition is always false for this single-row table.
> val withoutGroupBy = sqlContext.sql("""
>   SELECT 'foo'
>   FROM mytable
>   WHERE int_col == 0
> """)
> assert(withoutGroupBy.collect().isEmpty, "original query returned wrong answer")
> // After adding a 'GROUP BY 1' the query result should still be empty because we'd be grouping an empty table:
> val withGroupBy = sqlContext.sql("""
>   SELECT 'foo'
>   FROM mytable
>   WHERE int_col == 0
>   GROUP BY 1
> """)
> assert(withGroupBy.collect().isEmpty, "adding GROUP BY resulted in wrong answer")
> {code}
> Here, this fails the second assertion by returning a single row. It appears that running {{group by 1}} where column 1 is a constant causes filter conditions to be ignored.
> Both PostgreSQL and SQLite return empty result sets for the query containing the {{GROUP BY}}. 



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