wesleydeng created IMPALA-10323:
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Summary: 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 3.4.0
Environment: 3 nodes ( 24 core, 64 GB mem)
impala 3.4
Reporter: wesleydeng
Fix For: Impala 3.4.0, Impala 3.3.0, Impala 3.2.0
Attachments: image-2020-11-12-20-36-50-082.png,
image-2020-11-12-20-43-47-010.png
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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