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https://issues.apache.org/jira/browse/HIVE-16311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15959874#comment-15959874
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Matt McCline commented on HIVE-16311:
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Yes, OldHiveDecimal division is faster than new HiveDecimal because the new
code has to convert back and forth between BigDecimal whereas the old code
represented the decimal as BigDecimal. Due to the size of the Fast Decimal
change, we decided to defer division until later.
> Improve the performance for FastHiveDecimalImpl.fastDivide
> ----------------------------------------------------------
>
> Key: HIVE-16311
> URL: https://issues.apache.org/jira/browse/HIVE-16311
> Project: Hive
> Issue Type: Improvement
> Affects Versions: 2.2.0
> Reporter: Colin Ma
> Assignee: Colin Ma
> Fix For: 3.0.0
>
> Attachments: HIVE-16311.001.patch, HIVE-16311.002.patch,
> HIVE-16311.003.patch, HIVE-16311.004.patch, HIVE-16311.005.patch,
> HIVE-16311.withTrailingZero.patch
>
>
> FastHiveDecimalImpl.fastDivide is poor performance when evaluate the
> expression as 12345.67/123.45
> There are 2 points can be improved:
> 1. Don't always use HiveDecimal.MAX_SCALE as scale when do the
> BigDecimal.divide.
> 2. Get the precision for BigInteger in a fast way if possible.
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