[teiid-issues] [JBoss JIRA] (TEIID-2578) add/remove schema elements

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13309337#comment-13309337 ] 

Steven Hawkins commented on TEIID-2578:
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> and mark the imported metadata as READONLY and not allow any ALTER or persistent operations.

The side effect of supporting this style of import is that the vdb load becomes dependent upon services or we have to limit the import to only other ddl based vdbs and add logic to handle the load order.

> But if want to go towards the deployment based, we can simply provide *-vdb.ddl based deployer back into this without much hassle, but we would not support ALTERS on that.

That depends upon how far we want to go with these changes.  If the effect of deployment was simply to tie the deployment to an equivalent databasestore state, then alter would be supported.

Next changes:

- inverted the role of DatabaseStorage, so that DatabaseStore is primary.  Also combined PersistenceProxy and DatabaseStorage.
- implemented an undo/restore of a change if there is a metadata validation issue
- created a dummy command/plan to represent non-statement based ddl
- suppressed the cancel exception for ddl

Concerns:

- we need to address the potential consistency issues with alter to prevent the entire vdb / repository from becoming unusable.
- we may need to address the performance of metadata writes as eventually these files could grow to 10s of megabytes.
- databasestorage service has some wait cycles.  shouldn't it just be able to wait for services? 
- authorization is not checked for ddl operations

I think the best approach at this point is for me to push my changes to a common branch under teiid and we'll continue to iterate on things from there.

> add/remove schema elements
> --------------------------
>
>                 Key: TEIID-2578
>                 URL: https://issues.jboss.org/browse/TEIID-2578
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Query Engine
>            Reporter: Ramesh Reddy
>            Assignee: Ramesh Reddy
>             Fix For: 9.2
>
>
> Schemas are currently static after load.  Modifications can only happen with restarts or new versions.  We should allow add/drop at runtime.



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