[jira] [Updated] (KUDU-2380) Selective predicates when selecting high number of columns burns CPU in SerializeRowBlock

["Todd Lipcon (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KUDU-2380?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon updated KUDU-2380:
------------------------------
    Attachment: pprof.kudu-tserver.samples.cpu.001.pb.gz

> Selective predicates when selecting high number of columns burns CPU in SerializeRowBlock
> -----------------------------------------------------------------------------------------
>
>                 Key: KUDU-2380
>                 URL: https://issues.apache.org/jira/browse/KUDU-2380
>             Project: Kudu
>          Issue Type: Improvement
>          Components: tserver
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Major
>         Attachments: pprof.kudu-tserver.samples.cpu.001.pb.gz
>
>
> Testing a table with 280 columns, I found the following performance characteristic:
> - scanning all 280 columns with a selective non-key predicate which matches 0 rows took 8.28s
> - scanning no columns (count query) with the same predicate which matches 0 rows took 314ms.
> This suggests that we are burning 96% of our CPU doing useless work for this query.



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