[teiid-issues] [JBoss JIRA] (TEIID-2481) common table (with) push down improvements

[Mark Addleman (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12976728#comment-12976728 ] 

Mark Addleman commented on TEIID-2481:
--------------------------------------

FYI - Our most pressing need is projection minimization

> common table (with) push down improvements
> ------------------------------------------
>
>                 Key: TEIID-2481
>                 URL: https://issues.jboss.org/browse/TEIID-2481
>             Project: Teiid
>          Issue Type: Enhancement
>      Security Level: Public(Everyone can see) 
>          Components: Query Engine
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>             Fix For: 8.8
>
>
> The general strategy for with pushdown should better handle:
> - a with clause that can be pushed against a source that does not support common table.  If a single reference or some other sufficient condition is met then we should just inline the pushdown rather than inhibiting the whole query from pushing down.
> - even if a source supports with pushdown, it may be more performant in some circumstances to inline the common table reference (such as only a single reference).  This is complicated slightly by subqueries.
> - alternatively in some situations even if a with clause can be pushed, it may be better to not perform the pushdown -e.g. two separate pushdown accesses to a common table that is expensive to compute (this may need to be hint driven).



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