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Posted to issues@calcite.apache.org by "hqx (Jira)" <ji...@apache.org> on 2021/03/04 13:31:00 UTC

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

hqx created CALCITE-4522:
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             Summary: 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


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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