[jira] [Resolved] (CALCITE-4037) AggregateProjectMergeRule doesn't always respect column aliases

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

     [ https://issues.apache.org/jira/browse/CALCITE-4037?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde resolved CALCITE-4037.
----------------------------------
    Resolution: Won't Fix

Changing to 'won't fix'. We can continue discussion, and re-open if there is a consensus that we want to do this.

My position: we should strive to make rules generate better field names. But we can't commit to not changing field names. And sometimes we can't reach consensus on 'better'.

> AggregateProjectMergeRule doesn't always respect column aliases
> ---------------------------------------------------------------
>
>                 Key: CALCITE-4037
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4037
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: Sylvain Crozon
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: fix-AggregateProjectMergeRule.patch
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> When columns aggregated over are given an alias, but not aggregated values, the alias is lost: 
> {code:java}
> select deptno as x, sum(sal)
> from emp
> group by deptno
> {code}
> has the following plan
> {code:java}
> LogicalAggregate(group=[{0}], EXPR$1=[SUM($1)])
>   LogicalProject(X=[$7], SAL=[$5])
>     LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
>  which becomes  
> {code:java}
> LogicalAggregate(group=[{7}], EXPR$1=[SUM($5)])
>   LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
>  
> after the AggregateProjectMergeRule
>  
> I attempted a fix by comparing the row type's field names of the project node with its input, and skip merging with the agg node if they don't match. That works for the use case above, however that breaks quite a few unit tests. Some of them, I believe, should be updated like 
> testAggregateMerge1, the alias in the SQL queries are lost in the final plan. But for other use cases, mostly when there's a join, the simple column name comparison is not enough. 
>  
>  



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