[jira] [Issue Comment Deleted] (CALCITE-818) Multiple collation traits get wiped out when creating subset, thus cause unnecessary sort

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

     [ https://issues.apache.org/jira/browse/CALCITE-818?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde updated CALCITE-818:
--------------------------------
    Comment: was deleted

(was: If simplify is being called, it should use the most expressive trait (i.e. [)

> Multiple collation traits get wiped out when creating subset, thus cause unnecessary sort
> -----------------------------------------------------------------------------------------
>
>                 Key: CALCITE-818
>                 URL: https://issues.apache.org/jira/browse/CALCITE-818
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.4.0-incubating
>            Reporter: Maryann Xue
>            Assignee: Julian Hyde
>            Priority: Minor
>
> "select p1 from (values (2, 1)) as t(p0, p1)"
> or
> "select p0+p1 from (values (2, 1)) as t(p0, p1)"
> would return a plan (with VolcanoPlanner) like:
> {code}
> EnumerableSort(...)
>   EnumerableCalc(...)
>     EnumerableValues(...)
> {code}
> It was because a multiple collation trait was inferred from the LogicalValues rel as: [[0,1], [1]], and the LogicalProject would have a corresponding collation trait based on the project expressions. But when optimizing, the multiple collation trait was simplified to empty when a subset for the LogicalValues rel was created, thus making EnumerableCalc unable to infer collation accordingly.



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