[jira] [Resolved] (TAJO-341) Implement substr function

["Hyunsik Choi (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TAJO-341?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyunsik Choi resolved TAJO-341.
-------------------------------

    Resolution: Fixed

I've committed it to master branch. Thank you for your contributions.

> Implement substr function
> -------------------------
>
>                 Key: TAJO-341
>                 URL: https://issues.apache.org/jira/browse/TAJO-341
>             Project: Tajo
>          Issue Type: New Feature
>          Components: operator/function/udf
>            Reporter: Hyunsik Choi
>            Assignee: hyoungjunkim
>            Priority: Minor
>             Fix For: 0.8-incubating
>
>         Attachments: TAJO-341.patch
>
>
> h3. Function Definition
> {code}
> text substr(string text, from int4 [, count int4])
> {code}
> h3. Description
>  * It extracts substring (same as substring(string from from for count)). 
>  * If string is null, the result also should be null.
>  * Note that *from* is one based index.
>  * *from* can be negative integer.
>  * *count* can be omitted. If then, all string after *from* will be returned.
>  * *count* cannot be negative integer.
>  * If *count* is 0, the result should be '' instead of null.
> h3. Example and Sementic
> {code}
> hyunsik=> select substr('abcdef', 3, 2);
>  substr 
> --------
> cd
> (1 row)
> hyunsik=> select substr('abcdef',3) ;
>  substr 
> --------
>  cdef
> (1 row)
> hyunsik=> select substr('abcdef',1,1) ;
>  substr 
> --------
>  a
> (1 row)
> hyunsik=> select substr('abcdef',0,1) ;
>  substr 
> --------
>  
> (1 row)
> hyunsik=> select substr('abcdef',0,2) ;
>  substr 
> --------
>  a
> (1 row)
> {code}



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