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https://issues.apache.org/jira/browse/CALCITE-783?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14646100#comment-14646100
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Milinda Lakmal Pathirage commented on CALCITE-783:
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Hi [~maryannxue], I think you are right regarding this. It is my fault that I
blindly use LogicalAggregate's input's collation to infer aggregate's
collation. As you have mentioned inferring aggregate's collation is not that
straight forward. For tumbling windows based on group by to work, we just need
to properly infer project's trait set based on monotonicity metadata. I'll
create a JIRA ticket for this. Thanks for pointing 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
> Fix For: 1.4.0-incubating
>
> Attachments: CALCITE-783-0.patch, CALCITE-783-1.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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