[teiid-issues] [JBoss JIRA] (TEIID-1990) UNION pushdown

Wed Apr 4 11:22:47 EDT 2012

    [ https://issues.jboss.org/browse/TEIID-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681745#comment-12681745 ] 

Steven Hawkins commented on TEIID-1990:
---------------------------------------

Yes, that is the likely issue.  Teiid is adding a convert, but marking it as implicit so it is not immediately visible (this is for the benefit of designer).  Teiid 8.0 shows implicit conversion more clearly and also provides a mechanism for translators to declare support for only a subset of conversions.  This implicit conversion then is preventing pushdown.

It would be good to backport showing implicit conversion to 7.7.1 and to see why there wasn't a more specific message in the debug log.

> UNION pushdown
> --------------
>
>                 Key: TEIID-1990
>                 URL: https://issues.jboss.org/browse/TEIID-1990
>             Project: Teiid
>          Issue Type: Bug
>          Components: Query Engine
>    Affects Versions: 7.7
>            Reporter: Mark Addleman
>            Assignee: Steven Hawkins
>         Attachments: plan.txt, plan.txt
>
>
> I have SQL of the form
> SELECT a FROM (
>    SELECT a FROM ds.t1 UNION
>    SELECT a FROM ds.t2
> ) t
> The execution factory extends JDBCExecutionFactory and supports everything except row offset.  It appears that the two unioned SELECTs are being executed as separate statements rather than the entire unioned set being pushed down to the datasource.
> Attached is plan

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