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Posted to dev@hive.apache.org by "Johnny Zhang (JIRA)" <ji...@apache.org> on 2012/12/18 01:12:15 UTC
[jira] [Updated] (HIVE-3715) float and double calculation is
inaccurate in Hive
[ https://issues.apache.org/jira/browse/HIVE-3715?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Johnny Zhang updated HIVE-3715:
-------------------------------
Status: Patch Available (was: Open)
> float and double calculation is inaccurate in Hive
> --------------------------------------------------
>
> Key: HIVE-3715
> URL: https://issues.apache.org/jira/browse/HIVE-3715
> Project: Hive
> Issue Type: Bug
> Components: SQL
> Affects Versions: 0.10.0
> Reporter: Johnny Zhang
> Assignee: Johnny Zhang
> Attachments: HIVE-3715.patch.txt
>
>
> I found this during debug the e2e test failures. I found Hive miss calculate the float and double value. Take float calculation as an example:
> hive> select f from all100k limit 1;
> 48308.98
> hive> select f/10 from all100k limit 1;
> 4830.898046875 <--added 04875 in the end
> hive> select f*1.01 from all100k limit 1;
> 48792.0702734375 <--should be 48792.0698
> It might be essentially the same problem as http://effbot.org/pyfaq/why-are-floating-point-calculations-so-inaccurate.htm. But since e2e test compare the results with mysql and seems mysql does it right, so it is worthy fixing it in Hive.
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