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From Michael Bouschen <mbo.t...@spree.de>
Subject Re: Long running queries : timeout, and cancellation
Date Fri, 06 Feb 2009 17:58:47 GMT
Hi Andy,

I think this is a good idea and we should add this to the next release!

I agree to go for option 3 and add a method to the Query API to abort 
query execution. BTW, maybe abort is a better method name for the 
method, what do you think?

I'm wondering whether there are any implementation issues. AFAIK, there 
is no standard JDBC API to abort a a running JDBC query. So how about 
allowing the method to throw a JDOUnsupportedOptionException in case it 
cannot be implemented for the underlying database?

Could you please file a "New Feature" JIRA for this?

Regards Michael


> 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. Some ideas
>
> Option1 :
> 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
>
> Option2 :
> as Option1, plus setTimeout() on Query to define it on a per query basis.
>
> Option3 :
> as Option2, plus we add cancel() on Query so that users can cancel long 
> running queries programmatically, throwing a QueryInterruptedException 
> (extends JDOUserException). The cancel would apply to all currently running 
> invoked queries from that Query instance.
>
>
>
> I'd go for option 3 since it provides full control in one change and we won't 
> need to revisit the area later to add extra control. Comments ?
>
>   


-- 
*Michael Bouschen*
*Prokurist*

akquinet tech@spree GmbH
Bülowstr. 66, D-10783 Berlin

Fon:   +49 30 235 520-33
Fax:   +49 30 217 520-12
Email: michael.bouschen@akquinet.de
Url:    www.akquinet.de <http://www.akquinet.de>

akquinet tech@spree GmbH, Berlin
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