[teiid-issues] [JBoss JIRA] Resolved: (TEIID-942) Make ad hoc temp tables transactional

[Steven Hawkins (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-942?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steven Hawkins resolved TEIID-942.
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    Resolution: Done


Used table memory state cloning (persistent data is not cloned) to implement read isolation for mat views and rollback support for local temporary tables.  This was simpler than implementing full MVCC, but allows for less concurrency and there is additional overhead the larger the table.  The simplified concurrency is fine given we assume mat view updates are atomic - and performed outside of any running transaction and that the dominate use case for local temporary tables will be from a single transaction at a time.  The code will prevent local temporary tables from being modified outside of a pending transaction once they have been modified within the transaction - otherwise a rollback would lead to inconsistency.  Typically this scenario will not happen though as sharing the same connection / temporary tables across concurrent transactions should be rare.

Another drawback (which simplified the implementation) is that in a cloned state managedbatch removals are handled through garbage collection.  This may delay the reclaiming of buffer space and result in the unnecessary flushing of pages that may have otherwise already been removed. 


> Make ad hoc temp tables transactional
> -------------------------------------
>
>                 Key: TEIID-942
>                 URL: https://issues.jboss.org/browse/TEIID-942
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Query Engine
>    Affects Versions: 7.1
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>             Fix For: 7.6
>
>
> Ad hoc temp tables are scoped to the session and should be transactional.

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