[teiid-issues] [JBoss JIRA] (TEIID-1543) Add a query hint to limit the number of concurrent source queries

[Steven Hawkins (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-1543?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steven Hawkins updated TEIID-1543:
----------------------------------

    Fix Version/s:     (was: 8.3)
         Priority: Minor  (was: Major)


Added logic in 8.3 to make an explicit hint less of an issue.  The most common case this hint applies to is a limited union, so now the processing logic will detect this case and automatically reduce the parallelism based upon how tight the limit is.

In specific cases a hint may still be desirable, but the current implementation of the concurrency restriction is implemented at the request level and not at the plan level making it difficult to restrict concurrency effectively based upon the particulars of the plan.
                
> Add a query hint to limit the number of concurrent source queries
> -----------------------------------------------------------------
>
>                 Key: TEIID-1543
>                 URL: https://issues.jboss.org/browse/TEIID-1543
>             Project: Teiid
>          Issue Type: Sub-task
>          Components: Query Engine
>    Affects Versions: 7.4
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>            Priority: Minor
>
> We would like a new query hint to limit the number of parallel executions of union members. This is useful in two situations:
> 1. When the queries are expensive, but the overall union contains a limit that is most likely to be fulfilled by the first member of the union
> 2. When the queries are backed by a common resource which may be overloaded by multiple queries
> The addition of a hint would make this manageable by the client; perhaps something like "/*+ parallel=2*/"? 

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira