[jira] [Resolved] (CALCITE-4522) Sort cost should account for the number of columns in collation

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

     [ https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde resolved CALCITE-4522.
----------------------------------
    Resolution: Fixed

Fixed in [f4a5512c|https://github.com/apache/calcite/commit/f4a5512caeaf087147fec82b7d98ea231b134036]; thanks for the PR, [~871]!

> Sort cost should account for the number of columns in collation
> ---------------------------------------------------------------
>
>                 Key: CALCITE-4522
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4522
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: hqx
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 1.27.0
>
>          Time Spent: 9h 50m
>  Remaining Estimate: 0h
>
> 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.
>  # let heap_size be min(offset + fetch, input_count), and use input_count * max(1, log(heap_size))* row_byte to compute the cpu cost.



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