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https://issues.apache.org/jira/browse/FLINK-5520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15827772#comment-15827772
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ASF GitHub Bot commented on FLINK-5520:
---------------------------------------
Github user fhueske commented on the issue:
https://github.com/apache/flink/pull/3141
The difference between failing during validation and translation is the
code line that throws the exception. A check during validation causes an
exception on the line that is responsible for the error. A check during
translation throws an exception much later in the user program.
Regarding the check in the rule: IMO, each rule must ensure that is does
not translate the query into an invalid plan. It make sense though, to have an
additional safety check in the `DataSetJoin`. However, this check should be
done in the constructor and not in the `translateToPlan()` method (see
FLINK-5547) to fail fast if a rule tries to create an invalid plan.
> 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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