[teiid-issues] [JBoss JIRA] (TEIID-4100) Full odata expand support

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-4100?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13278780#comment-13278780 ] 

Steven Hawkins commented on TEIID-4100:
---------------------------------------

The approach that seems simplest here is to fetch the expanded entities inline using subqueries of the form:

select parent cols ... (select array_agg((child cols)) [order by] from child ...), (select array_agg ...) ...

This will create a tree of arrays that can be walked similar to the parent result set.  This will not be as performant as the join approach for a single expand child, so there may need to be some thought put into converting a single subquery into a join (which we currently do for subqueries in the where clause).

> Full odata expand support
> -------------------------
>
>                 Key: TEIID-4100
>                 URL: https://issues.jboss.org/browse/TEIID-4100
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: OData
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>             Fix For: 9.1
>
>
> To move TEIID-3039 we need to have xml document model style processing for expand support.  That is top down generation that supports arbitrary descendants - with targeted optimizations for projection minimization and dependent joins.



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