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Posted to issues-all@impala.apache.org by "Philip Zeyliger (JIRA)" <ji...@apache.org> on 2018/10/30 19:12:00 UTC
[jira] [Commented] (IMPALA-7785) GROUP BY clause cannot contain a
CASE statement
[ https://issues.apache.org/jira/browse/IMPALA-7785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16669216#comment-16669216 ]
Philip Zeyliger commented on IMPALA-7785:
-----------------------------------------
Hi Paul!
I tried this on a recent (two weeks old?) build and didn't have any trouble:
{code}
[localhost:21000] default> select CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END from functional.alltypes group by CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END limit 1;
Query: select CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END from functional.alltypes group by CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END limit 1
Query submitted at: 2018-10-30 12:10:49 (Coordinator: http://12987a4df8d5:25000)
Query progress can be monitored at: http://12987a4df8d5:25000/query_plan?query_id=6346330a763f4efb:8773638300000000
+-----------------------------------------------------------------+
| case when string_col is not null then string_col else 'foo' end |
+-----------------------------------------------------------------+
| 8 |
+-----------------------------------------------------------------+
Fetched 1 row(s) in 5.06s
{code}
Are you sure this isn't happening because of a change you have on your branch?
> GROUP BY clause cannot contain a CASE statement
> -----------------------------------------------
>
> Key: IMPALA-7785
> URL: https://issues.apache.org/jira/browse/IMPALA-7785
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 3.0
> Reporter: Paul Rogers
> Priority: Minor
>
> The FE cannot handle a {{CASE}} statement in a {{GROUP BY}} clause. As a result, the change in IMPALA-7655 cannot be applied to queries with such a clause for fear of ending up in the situation shown later.
> Consider this simple query:
> {code:sql}
> SELECT coalesce(string_col, 'foo')
> FROM functional.alltypes
> GROUP BY coalesce(string_col, 'foo')
> {code}
> The above will fail with the following:
> {noformat}
> org.apache.impala.common.AnalysisException:
> select list expression not produced by aggregation output
> (missing from GROUP BY clause?) :
> CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END
> {noformat}
> This then causes the rewrites in IMPALA-7655 to fail:
> {code:sql}
> SELECT coalesce(string_col, 'foo')
> FROM functional.alltypes
> GROUP BY coalesce(string_col, 'foo')
> {code}
> The above is rewritten using the new conditional function rewrite rules. Result:
> {noformat}
> org.apache.impala.common.AnalysisException:
> select list expression not produced by aggregation output
> (missing from GROUP BY clause?):
> CASE WHEN string_col IS NOT NULL THEN string_col ELSE 'foo' END
> {noformat}
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