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https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17296425#comment-17296425
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hqx commented on CALCITE-4522:
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Thanks, I modify the issue description more detailed. I suggest the follow
formula because we can use heap sort if offset + fetch < input_count, else use
heap sort, quick sort and so on.
min(offset + fetch, input_count) * log(input_count)* row_byte
> 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 the RelCollation is empty, there is no need to sort, but it still
> compute the cpu cost of sort.
> # use n * log\(n) * row_byte to estimate the cpu cost may be inaccurate,
> where n means the output row count of the sort operator, and row_byte means
> the average bytes of one row .
> Instead, I give follow suggestion.
> # the cpu cost is zero if the RelCollation is empty.
> # use min(offset + fetch, input_count) * log\(input_count)* row_byte to
> compute the cpu cost.
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