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https://issues.apache.org/jira/browse/HIVE-16311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15947130#comment-15947130
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Matt McCline commented on HIVE-16311:
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Well, now wait a minute. That document references a very old JIRA. I haven't
seen this document before. I'm drawing in [~jdere] because he recently worked
with precision / scale issues with multiplication. I'd like to understand why
the scale was being limited to 6. I'm not willing to blindly go back without
understanding why the change was made when BigDecimal was presumably introduced.
The old HiveDecimal introduced with Apr 9, 2013 HIVE-4271 : :Limit precision of
decimal type (Gunther Hagleitner via A…
…shutosh Chauhan)" that began using BigDecimal. I haven't found the older
version yet.
> 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
>
>
> 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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