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https://issues.apache.org/jira/browse/IMPALA-10323?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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wesleydeng resolved IMPALA-10323.
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Fix Version/s: Impala 4.0
Resolution: Fixed
> use snprintf instead of lexical_cast when casting int to string, to improve
> multi-thread performance
> -----------------------------------------------------------------------------------------------------
>
> Key: IMPALA-10323
> URL: https://issues.apache.org/jira/browse/IMPALA-10323
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Affects Versions: Impala 3.1.0, Impala 3.2.0, Impala 3.3.0, Impala 3.4.0
> Environment: 3 nodes ( 24 core, 64 GB mem)
> impala 3.4
> Reporter: wesleydeng
> Assignee: wesleydeng
> Priority: Major
> Fix For: Impala 4.0
>
> Attachments: image-2020-11-12-20-36-50-082.png,
> image-2020-11-12-20-43-47-010.png
>
> Original Estimate: 12h
> Remaining Estimate: 12h
>
> For float_type, lexical_cast is replace by snprintf （issue
> https://issues.apache.org/jira/browse/IMPALA-1738），but why not do the same
> replacement for num_type.
> Test is done in 2 sql case :
> 1) *group by cast int to string* :
> select cast(f1 as string) as kk, count ( * ) from test.my_table group by kk;
> 2) *group by* *int :*
> select f1 as kk, count( * ) from test.my_table group by kk;
> !image-2020-11-12-20-43-47-010.png!
> from the benchmark, we can see that performance decreased seriously with more
> thread.
> But using snprintf, performance improved significantly with more thread .
>
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