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Posted to dev@hive.apache.org by "Ashutosh Chauhan (JIRA)" <ji...@apache.org> on 2013/01/07 19:50:13 UTC
[jira] [Commented] (HIVE-3773) Share input scan by unions across
multiple queries
[ https://issues.apache.org/jira/browse/HIVE-3773?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13546139#comment-13546139 ]
Ashutosh Chauhan commented on HIVE-3773:
----------------------------------------
Isn't this already implemented in HIVE-2206 ?
> Share input scan by unions across multiple queries
> --------------------------------------------------
>
> Key: HIVE-3773
> URL: https://issues.apache.org/jira/browse/HIVE-3773
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Gang Tim Liu
>
> Consider a query like:
> select * from
> (
> select key, 1 as value, count(1) from src group by key
> union all
> select 1 as key, value, count(1) from src group by value
> union all
> select key, value, count(1) from src group by key, value
> ) s;
> src is scanned multiple times currently (one per sub-query).
> This should be treated like a multi-table insert by the optimizer.
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