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From "Jihoon Son (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TAJO-391) Change setting default type in query from FLOAT4 to FLOAT8
Date Fri, 06 Dec 2013 16:51:35 GMT

    [ https://issues.apache.org/jira/browse/TAJO-391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13841407#comment-13841407
] 

Jihoon Son commented on TAJO-391:
---------------------------------

Right, but the precision problem is also occurred when we use float8. 
To store the exact floating point value, we should use other types such as BigDecimal which
significantly degrade the performance. 

If we have to get the exact results, we can accept those overheads. 
However, the difference of sine values from float4 and float8 is very small, and I think that
it can be currently ignored.

> Change setting default type in query from FLOAT4 to FLOAT8
> ----------------------------------------------------------
>
>                 Key: TAJO-391
>                 URL: https://issues.apache.org/jira/browse/TAJO-391
>             Project: Tajo
>          Issue Type: Improvement
>            Reporter: DaeMyung Kang
>            Assignee: DaeMyung Kang
>            Priority: Minor
>         Attachments: TAJO-391.patch
>
>
> FLOAT4 is default parsed float type in tajo.
> but it can cause some trobles when we use it as FLOAT8.
> for examples.
> 0.4(f) will changed to 0.40000000000005(d)
> so it cause different result from java.Math functions.



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