You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues@calcite.apache.org by "Julian Hyde (Jira)" <ji...@apache.org> on 2021/03/28 04:15:00 UTC
[jira] [Updated] (CALCITE-4522) CPU cost of Sort should be lower if
sort keys are empty
[ https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Julian Hyde updated CALCITE-4522:
---------------------------------
Summary: CPU cost of Sort should be lower if sort keys are empty (was: Sort cost should account for the number of columns in collation)
> 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.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)