[jira] [Commented] (QUICKSTEP-118) Optimization Rule For Union of same subqueries

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/QUICKSTEP-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16447026#comment-16447026 ] 

Julian Hyde commented on QUICKSTEP-118:
---------------------------------------

Only valid if int_col is unique.

> Optimization Rule For Union of same subqueries
> ----------------------------------------------
>
>                 Key: QUICKSTEP-118
>                 URL: https://issues.apache.org/jira/browse/QUICKSTEP-118
>             Project: Apache Quickstep
>          Issue Type: Improvement
>          Components: Query Optimizer
>            Reporter: Zuyu Zhang
>            Priority: Minor
>
> Currently, [the following query|https://github.com/apache/incubator-quickstep/blob/master/query_optimizer/tests/physical_generator/Select.test#L3156] is convert into a `UnionAll` followed by `Aggregate` for de-duplication.
> {code:java}
> SELECT int_col FROM test
> UNION
> SELECT int_col FROM test;
> {code}
>  
> The optimizer should, however, transform such query into a simple select query:
> {code:java}
> SELECT int_col FROM test;
> {code}



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