[teiid-issues] [JBoss JIRA] Commented: (TEIID-1326) API request: rewrite query/command before it reaches the teiid planner

Wed Apr 6 14:28:33 EDT 2011

    [ https://issues.jboss.org/browse/TEIID-1326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12594101#comment-12594101 ] 

Steven Hawkins commented on TEIID-1326:
---------------------------------------

I should add that this approach has several advantages over the current direct manipulation of Table metadata records (possibly through ddl).

1. that the view definitions can be made user specific, without api changes to the metadata classes.
2. a single class can be consulted which can simplify updating the same view across multiple vdb versions. 
3. dml or a single instance administrative call would need to made on each member in a cluster (we may address this through a live operational repository in the future)
4. related to number 3, changes to the metadata records are not-persistent.

So having this metadata update or costing updates, etc. through a real operational repository with notifications can be a long term direction, but for now we'll have to settle.

> API request:  rewrite query/command before it reaches the teiid planner
> -----------------------------------------------------------------------
>
>                 Key: TEIID-1326
>                 URL: https://issues.jboss.org/browse/TEIID-1326
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Query Engine
>    Affects Versions: 7.1
>            Reporter: Mark Addleman
>            Assignee: Steven Hawkins
>             Fix For: 7.4
>
>
> I'd like an API to inspect and rewrite a user query/command before it reaches the Teiid planner. The use case is to rewrite the query/command to implement view-like capabilities.  For example:
> SELECT a,b,c FROM table1 AS t WHERE t.a='xyz'  would be rewritten as:
> SELECT a,b,c FROM (SELECT a,b,c FROM table2 UNION SELECT a,b,c FROM table3) AS t
> I imagine this API would be similar to the translator API:  it would receive a data structure representing the query/command and use a visitor to rewrite the query.  As a convenience, it would be nice to have something similar to the SQLConversionVisitor.

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