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From "Craig Russell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JDO-623) Query cancel and timeout support
Date Mon, 09 Feb 2009 19:16:59 GMT

    [ https://issues.apache.org/jira/browse/JDO-623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12671967#action_12671967
] 

Craig Russell commented on JDO-623:
-----------------------------------

> Since Query.cancel() cannot be invoked from the thread which started the execution, should
PM.setMultithreaded(true) be invoked ? 

No, multithreaded is intended to require that the implementation protect data structures from
harm in case multiple threads are active in data structures visible to the application. Query.cancel
doesn't operate on visible data structures.

> If setMultithreaded(true) is mandatory, should cancel() throw an Exception if multithreaded
flag is false? 

No.

> Is it the case to handle Query.cancel() without multithreaded flag being true ?

Yes. Since the thread that is stuck in a query can't be simultaneously modifying data structures,
normal care is all that's needed by the implementation to avoid corruption.



> Query cancel and timeout support
> --------------------------------
>
>                 Key: JDO-623
>                 URL: https://issues.apache.org/jira/browse/JDO-623
>             Project: JDO
>          Issue Type: New Feature
>          Components: api2, tck2
>            Reporter: Andy Jefferson
>            Assignee: Andy Jefferson
>             Fix For: JDO 2 maintenance release 3
>
>         Attachments: query_timeout.patch
>
>
> JDO doesn't have a mechanism to stop queries from overrunning. JPA2 now allows 
> a persistence property to allow timing them out, and most JDO implementations 
> have allowed this as an extension since JDO1. It would make sense for JDO 
> (2.3) to have the same or a variation. I propose having the following
> Simple PMF property "javax.jdo.option.queryTimeout" to specify the number of millisecs
(or secs) before any query is timed out. Throw a QueryTimeoutException (extends JDOException)
when the timeout happens.
> Add methods Query.setTimeout(int), Query.getTimeout() to allow setting/retrieving the
timeout interval on a per-query basis.
> Add method Query.cancel() to cancel any running query. If an implementation doesn't support
cancelling of queries then it should throw a JDOUnsupportedOptionException. Any query execute()
that is cancelled will throw a QueryInterruptedException (extends JDOUserException).

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