[jira] [Comment Edited] (CALCITE-4522) optimize sort cost formula

["hqx (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17295696#comment-17295696 ] 

hqx edited comment on CALCITE-4522 at 3/5/21, 1:59 AM:
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[~julianhyde] hi

there is no need to sort, I mean the Relcollation#fieldCollations is empty.

I have make a pr, you may help me review it at  [https://github.com/apache/calcite/pull/2363
|https://github.com/apache/calcite/pull/2363|

 


was (Author: 871):
[~julianhyde] hi

there is no need to sort, I mean the Relcollation#fieldCollations is empty.

I have make a pr, you may help me review it at  [https://github.com/apache/calcite/pull/2363
|https://github.com/apache/calcite/pull/2363,]

 

> optimize sort cost formula
> --------------------------
>
>                 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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