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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-591) create new type of join ( 1 row for a given key from multiple tables)
Date Thu, 10 Sep 2009 02:09:57 GMT

    [ https://issues.apache.org/jira/browse/HIVE-591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753380#action_12753380

Namit Jain commented on HIVE-591:


The following lines are not needed

3079		  if(opParseCtx == null) throw new SemanticException("ctx");
3080 		  if(child == null) throw new SemanticException("diteto");
3081 		  if(opParseCtx.get(child) == null) throw new SemanticException("child "+child.toString());

Can you add more comments in CommonJoinOperator about the semantics of preserve etc. ?

Otherwise, it looks good

> create new type of join ( 1 row for a given key from multiple tables)
> ---------------------------------------------------------------------
>                 Key: HIVE-591
>                 URL: https://issues.apache.org/jira/browse/HIVE-591
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Emil Ibrishimov
>         Attachments: HIVE-591.1.patch, HIVE-591.2.patch, HIVE-591.3.patch
> It will be useful to support a new type of join:
> say:
> select .. from JOIN TABLES (A,B,C) WITH KEYS (A.key, B.key, C.key) where ....
> The semantics are that for a given key only 1 row is created - nulls are present for
the the tables which do not contain a row for that key.
> There is no limit on the number of tables, the number of keys should be the same as the
number of tables.

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