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From "Adam Kramer (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-832) Disallow OUTER JOIN with partition in WHERE clause in strict mode
Date Tue, 15 Sep 2009 02:21:57 GMT
Disallow OUTER JOIN with partition in WHERE clause in strict mode
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                 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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