[jira] [Commented] (CALCITE-1450) support a UDTF replicate_rows

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-1450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15583861#comment-15583861 ] 

Julian Hyde commented on CALCITE-1450:
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It would be useful if {{replicate_rows}} were a relational operator (i.e. a subclass of {{RelNode}}), not a UDTF. Then we could write rules to push {{Filter}} and {{Project}} operators through it, and we wouldn't necessarily have to implement it in Java.

> support a UDTF replicate_rows
> -----------------------------
>
>                 Key: CALCITE-1450
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1450
>             Project: Calcite
>          Issue Type: Sub-task
>            Reporter: Pengcheng Xiong
>            Assignee: Julian Hyde
>
> Add a user-defined table function that has a count column N, and a number of other columns, and for each row, produces N copies of that row.
> The purpose of this table function is to implement {{INTERSECT ALL}} and {{EXCEPT ALL}}. Observe that if have a table 'five' with 5 rows with the value 'x', and a table 'three' with 3 rows with the value 'x', then {{five INTERSECT ALL three}} will need to emit {{min(5, 3))}} rows, and {{five EXCEPT ALL three}} will emit {{5 - 3}} rows.



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