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

Tue Apr 3 21:42:47 EDT 2012

    [ https://issues.jboss.org/browse/TEIID-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681465#comment-12681465 ] 

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

The debug log shows that only some of the access nodes have been raised above their parent project nodes after RuleRaiseAccess.  The most likely reason is that the source does not support projecting non-column reference expressions.  See ExecutionFactory.supportsSelectExpression.  We should though add a debug line to the debug log stating why the pushdown has been prevented, which is typically done for criteria pushing but has not yet been added for all other situations.

> UNION pushdown
> --------------
>
>                 Key: TEIID-1990
>                 URL: https://issues.jboss.org/browse/TEIID-1990
>             Project: Teiid
>          Issue Type: Bug
>            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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