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From "Kurt Young (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-5266) Eagerly project unused fields when selecting aggregation fields
Date Wed, 07 Dec 2016 09:46:58 GMT

    [ https://issues.apache.org/jira/browse/FLINK-5266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15728297#comment-15728297

Kurt Young commented on FLINK-5266:

You mean "Aggregate.construct()"? 

Hmm..I didn't think about that, yet. My current approach is adding some extra logic when we
selecting fields out of the table. Let me think about both approaches through and compare
the differences and get back to you.

> Eagerly project unused fields when selecting aggregation fields
> ---------------------------------------------------------------
>                 Key: FLINK-5266
>                 URL: https://issues.apache.org/jira/browse/FLINK-5266
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>            Reporter: Kurt Young
>            Assignee: Kurt Young
> When we call table's {{select}} method and if it contains some aggregations, we will
project fields after the aggregation. Would be better to project unused fields before the
aggregation, and can furthermore leave the opportunity to push the project into scan.
> For example, the current logical plan of a simple query:
> {code}
> table.select('a.sum as 's, 'a.max)
> {code}
> is
> {code}
> LogicalProject(s=[$0], TMP_2=[$1])
>   LogicalAggregate(group=[{}], TMP_0=[SUM($5)], TMP_1=[MAX($5)])
>     LogicalTableScan(table=[[supplier]])
> {code}
> Would be better if we can project unused fields right after scan, and looks like this:
> {code}
> LogicalProject(s=[$0], EXPR$1=[$0])
>   LogicalAggregate(group=[{}], EXPR$1=[SUM($0)])
>     LogicalProject(a=[$5])
>       LogicalTableScan(table=[[supplier]])
> {code}

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