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

["Maryann Xue (JIRA)" <ji...@apache.org>]

Maryann Xue created CALCITE-818:
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             Summary: 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)"
<p>
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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