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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-262) outer join gets some duplicate rows in some scenarios
Date Sat, 31 Jan 2009 23:29:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-262?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12669286#action_12669286

Namit Jain commented on HIVE-262:

Ashish suggested the following approach:

Based on join conditions, create a set of all tables being joined (no outer join), and if
one of them is null for a given value, all of them become null.

For example,

A join B on A.c1=B.c1 join C on A.c1=C.c1 right outer join D on A.c1=D.c1

A,B,C belong to the same group (since A joins with B and A joins with C).

So, for a given key (c1), if there is no row corresponding to either of A, B, or C - assume
there is no row for all of them for that key.

That works for the example above, and the approach is different from the patch

> outer join gets some duplicate rows in some scenarios
> -----------------------------------------------------
>                 Key: HIVE-262
>                 URL: https://issues.apache.org/jira/browse/HIVE-262
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>    Affects Versions: 0.2.0
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>            Priority: Blocker
>             Fix For: 0.2.0
>         Attachments: patch.262.1.txt, patch262.2.txt
> SELECT * FROM src src1 JOIN src src2 ON (src1.key = src2.key AND src1.key < 10) RIGHT
OUTER JOIN src src3 ON (src1.key = src3.key AND src3.key < 20);
> returns duplicate rows for outer join

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