[TAJO-341] Implement substr function

• Type: New Feature
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.8.0
• Component/s: Function/UDF
• Assignee: Hyoungjun Kim
• Reporter: Hyunsik Choi
• Created: 29/Nov/13 09:21
• Updated: 30/Nov/13 06:06
• Resolved: 30/Nov/13 05:55

Description

Function Definition

text substr(string text, from int4 [, count int4])

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.

Example and Sementic

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)

Issue Links

• relates to: TAJO-344 Tajo cannot recognize negative numeric expressions