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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-5520) Disable outer joins with non-equality predicates
Date Thu, 19 Jan 2017 16:39:26 GMT

    [ https://issues.apache.org/jira/browse/FLINK-5520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15830222#comment-15830222
] 

ASF GitHub Bot commented on FLINK-5520:
---------------------------------------

Github user lincoln-lil commented on the issue:

    https://github.com/apache/flink/pull/3141
  
    @fhueske when I add more test cases for "outer joins" with local predicates, I found different
limitations between tableAPI and SQL, e.g., "SELECT c, g FROM Table3 left outer join Table5
on a = d AND e < 3" is valid, but dsFromTuple3.leftOuterJoin(dsFromTuple5, 'a === 'd &&
'e < 3) is invalid, because validation in Join node sees original join predicates and validates
simply, while in DataSetJoinRule the join predicates could be pruned according to the equivalence
in relational algebra. 
    I have a question, should we keep the tableAPI consistent with SQL? If so, the validation
in tableAPI will be much more complex, and it reminds me the previous discussion about validation
either in one or two places.  Or just maintain the current implementation unchanged, because
we will add support for both FLINK-5498 and FLINK-5511 soon, then these differences will be
eliminated.
    What do you think ?



> Disable outer joins with non-equality predicates
> ------------------------------------------------
>
>                 Key: FLINK-5520
>                 URL: https://issues.apache.org/jira/browse/FLINK-5520
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API & SQL
>    Affects Versions: 1.2.0
>            Reporter: Fabian Hueske
>            Assignee: lincoln.lee
>            Priority: Blocker
>             Fix For: 1.2.0
>
>
> Outer joins with non-equality predicates (and at least one equality predicate) compute
incorrect results. 
> Since this is not a very common requirement, I propose to disable this feature for the
1.2.0 release and correctly implement it for a later version.
> The fix should add checks in the Table API validation phase (to get a good error message)
and in the DataSetJoinRule to prevent translation of SQL queries with non-equality predicates
on outer joins.



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