[teiid-issues] [JBoss JIRA] Resolved: (TEIID-1422) Limit pushing can result in inconsistent xml results

[Steven Hawkins (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-1422?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steven Hawkins resolved TEIID-1422.
-----------------------------------

    Resolution: Done


updated the limit pushing logic to not push the limit below points where the cardinality may be affected after the limit.

> Limit pushing can result in inconsistent xml results
> ----------------------------------------------------
>
>                 Key: TEIID-1422
>                 URL: https://issues.jboss.org/browse/TEIID-1422
>             Project: Teiid
>          Issue Type: Bug
>          Components: Query Engine
>    Affects Versions: 6.0.0
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>            Priority: Critical
>             Fix For: 7.1.1, 7.3
>
>
> A customer case (00393370) was using rowlimitexception and not actually triggering the exception when expected.   This is due to our logic in rulepushlimit that allows an unordered limit to be pushed through union not all, select nodes, or dup removal.  While the results may be consistent for some ordering of results there are many situations when you will get back far less results than the limit specifies.  The intent was to more broadly push the limit rather than to apply it in a fully consistent manner.  However this is problematic for situations, like the rowlimitexception logic that expect an exceptional condition to be triggered if the limit is exceeded.
> The best fix would be to just not push an unordered limit in these situations, then if the more aggressive pushing is desired by a user we can look at using a hint or some other mechanism to allow the pushing.

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