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Posted to issues@calcite.apache.org by "hqx (Jira)" <ji...@apache.org> on 2021/03/05 17:42:00 UTC

[jira] [Commented] (CALCITE-4522) Sort operator returns the same cpu cost no matter the RelCollation is empty or not

    [ https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17296229#comment-17296229 ] 

hqx commented on CALCITE-4522:
------------------------------

I will do it

> Sort operator returns the same cpu cost no matter the RelCollation is empty or not
> ----------------------------------------------------------------------------------
>
>                 Key: CALCITE-4522
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4522
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: hqx
>            Priority: Minor
>
> The old method to compute the cost of sort has some problem.
>  # when there is no need to sort, it still to compute the cpu cost of sort.
>  # use n * log\(n) * rowBytes to estimate the cpu cost may be inaccurate, where n means the output row count of the sort operator, and rowBytes means the average bytes of one row .
> Instead, I give follow suggestion.
>  # the cpu cost is zero if there is no need to sort.
>  # use m * log\(n)* rowBytes to compute the cpu cost, where m is the sum of offset + limit and n means input row count.



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