Details
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Improvement
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Status: Resolved
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Major
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Resolution: Fixed
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Impala 3.1.0, Impala 3.2.0, Impala 3.3.0, Impala 3.4.0
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None
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3 nodes ( 24 core, 64 GB mem)
impala 3.4
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ghx-label-3
Description
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;
from the benchmark, we can see that performance decreased seriously with more thread.
But using snprintf, performance improved significantly with more thread .