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From "Ashish Thusoo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-179) SUBSTR function should work like other databases
Date Fri, 09 Jan 2009 15:22:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12662395#action_12662395

Ashish Thusoo commented on HIVE-179:

The patch looks correct and rather harmless. I tried the change that you suggested to groupby2_map.q
on a clean branch and it worked find. If you are getting a cast exception it is likely related
to the change of signatures but even that seems harmless. Trying out this patch in my environment

> SUBSTR function should work like other databases
> ------------------------------------------------
>                 Key: HIVE-179
>                 URL: https://issues.apache.org/jira/browse/HIVE-179
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: David Phillips
>            Assignee: David Phillips
>            Priority: Critical
>         Attachments: hive-substr.patch
> Positions start at 1, not 0.  Negative positions start at the end of the string and count
> Oracle returns null for lengths less than 1 or non-existent substrings (any empty strings
are null).  MySQL and PostgreSQL return empty strings, never null.  PostgreSQL errors for
negative lengths.  I suggest we follow the MySQL behavior.
> Oracle treats position 0 the same as 1.  Perhaps we should too?
> {noformat}
>      SUBSTR('ABC',1,1): A
> MySQL:
>      SUBSTR('ABC',0,1): <empty>
>      SUBSTR('ABC',0,2): <empty>
>      SUBSTR('ABC',1,0): <empty>
>     SUBSTR('ABC',1,-1): <empty>
> Oracle:
>      SUBSTR('ABC',0,1): A
>      SUBSTR('ABC',0,2): AB
>      SUBSTR('ABC',1,0): <null>
>     SUBSTR('ABC',1,-1): <null>
> {noformat}

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