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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-832) Disallow OUTER JOIN with partition in WHERE clause in strict mode
Date Tue, 15 Sep 2009 18:04:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755613#action_12755613
] 

Namit Jain commented on HIVE-832:
---------------------------------

Yes, but there was a usecase when this was being used to do perform subtraction (A - B).


> Disallow OUTER JOIN with partition in WHERE clause in strict mode
> -----------------------------------------------------------------
>
>                 Key: HIVE-832
>                 URL: https://issues.apache.org/jira/browse/HIVE-832
>             Project: Hadoop Hive
>          Issue Type: Wish
>            Reporter: Adam Kramer
>
> There is a wide-range poorly-understood issue in how WHERE and ON clauses work in the
case of outer joins.
> The WHERE filter is applied after the join. After an outer join, the INNER table (the
left table in a RIGHT OUTER, or the left table in the LEFT OUTER) has all columns set to NULL
for all rows. As a result, if ANY of them are cited in the WHERE clause, they will equal NULL.
This almost always causes the join to effectively be an INNER join, even though the user typed
the word O-U-T-E-R, probably for good reason.
> In strict mode, we should not allow ANY COLUMNS from the inner table to appear in the
WHERE clause.

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