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https://issues.apache.org/jira/browse/CALCITE-818?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14643523#comment-14643523
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Maryann Xue edited comment on CALCITE-818 at 7/27/15 10:45 PM:
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I think the unordered query case is exactly about the "top down" thing, the
consumer shouldn't have asked for a trait it does not need, i.e., unordered
queries should clear the collation trait when it realizes it does not need it.
During conversion from SqlNode to Logical rels, the collation trait is inferred
in the "create()" method of Logical rels. Other rels' traits won't matter here
but the top node does.
was (Author: maryannxue):
I think the unordered query case is exactly about the "top down" thing, the
consumer shouldn't have asked for a trait it does not need, i.e., unordered
queries should clear the collation trait when it realizes it does not need it.
> 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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