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From "Hyunsik Choi (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (TAJO-391) Change setting default type in query from FLOAT4 to FLOAT8
Date Sat, 07 Dec 2013 04:31:37 GMT

    [ https://issues.apache.org/jira/browse/TAJO-391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13842070#comment-13842070
] 

Hyunsik Choi edited comment on TAJO-391 at 12/7/13 4:30 AM:
------------------------------------------------------------

To deal with exact real numbers throughout query processing, Tajo has to support *numeric*
type and lots of functions that takes numeric types as parameters. However, currently, Tajo
does not have them. Even though Tajo uses more precise types (e.g., BigDecimal), it will lost
precision during passing functions and operations. I think that, in this time, parsing real
values via FLOAT8 is a realistic solution because FLOAT8 is the most precise real value type
in Tajo.


was (Author: hyunsik):
To deal with exact real numbers throughout query processing, Tajo has to support *numeric*
type and lots of functions that takes numeric types as parameters. However, currently, Tajo
does not have them. Even though Tajo use more precise types (e.g., BigDecimal), it will lost
precision during passing functions and operations. I think that, in this time, parsing real
values via FLOAT8 is a realistic solution because FLOAT8 is the most precise real value type
in Tajo.

> 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
>          Components: operator/function/udf
>            Reporter: DaeMyung Kang
>            Assignee: DaeMyung Kang
>            Priority: Minor
>             Fix For: 0.8-incubating
>
>         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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