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https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317762#comment-17317762
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Vladimir Sitnikov commented on CALCITE-4522:
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[~rubenql], the cost formulas are literally all wrong, see
https://lists.apache.org/thread.html/a038e66943b9c4bcb8dfac8130c7d7c9d47b455788af335ba7f202bc%40%3Cdev.calcite.apache.org%3E
For instance, {{EnumerableHashJoin}} uses {{nLogN}} which is, well, quite a
weird function for a hash join.
> CPU cost of Sort should be lower if sort keys are empty
> -------------------------------------------------------
>
> 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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