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https://issues.apache.org/jira/browse/TAJO-391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13842201#comment-13842201
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DaeMyung Kang commented on TAJO-391:
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[~jihoonson]
Actually I didn't mean "every real value should be float8". I am sorry to make
you confused.
I investigated some other dbms's operations(mysql, postgresql)
They parsed floating point type as double in query.((not mean select query from
table.it is always determined)
so. below example show the behaviors;
#postgresql
create table tbl_test(a real);
insert into tbl_test values(0.4);
select cbrt(a) from tbl_test1;
===> 0.736806303387834
create table tbl_test2(a float);
insert into tbl_test2 values(0.4);
select cbrt(a) from tbl_test2;
===> 0.736806299728077
select cbrt(0.4);
===> 0.736806299728077
but tajo just parse floating point type as float4.
so.it always causes upper casting to Float8 in some functions.
I want to point out this :) Thank you for advice :)
> 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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