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https://issues.apache.org/jira/browse/CALCITE-783?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14616150#comment-14616150
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Milinda Lakmal Pathirage commented on CALCITE-783:
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[~julianhyde], I'll finish the RelMdCollaiton.project. Thanks for looking into
this.
> Infer collation of Project using monotonicity
> ---------------------------------------------
>
> Key: CALCITE-783
> URL: https://issues.apache.org/jira/browse/CALCITE-783
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Milinda Lakmal Pathirage
> Assignee: Julian Hyde
> Attachments: CALCITE-783-0.patch
>
>
> Current implementation of RelMdCollation#project doesn't handle function
> expressions and because of that we loose any collation metadata related to
> monotonic expressions which can be useful for generating streaming query
> execution plans involving tumbling windows.
> Following is how current code looks like (RelMdCollation):
> 185: for (Ord<RexNode> project : Ord.zip(projects)) {
> 186: if (project.e instanceof RexInputRef) {
> 187: targets.put(((RexInputRef) project.e).getIndex(), project.i);
> 188: }
> 189: }
> We only handle projects of type RexInputRef. But to support monotonic
> expressions we should laso handle projects of type RexCall.
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