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From Marc Prud'hommeaux <mprud...@apache.org>
Subject Re: How to turn off sub-selects in updates?
Date Sat, 17 Mar 2007 17:43:35 GMT
Dave-

> I'm using 5.0.27-standard, so perhaps that bug is not the problem --
> or it wasn't fixed.

If it's not working for MySQL 5, can you file an OpenJPA JIRA report  
for this at https://issues.apache.org/jira/browse/OPENJPA ? We should  
probably try to figure out some way to work around the limitation.


> Is it possible to turn off OpenJPA generated sub-selects and only do a
> sub-select when an application query uses one? That's the default
> behavior in Toplink/JPA.

If you set the DBDictionary parameter to SupportsSubselect=false,  
then we won't generate the subselect (although we'll probably just  
wind up having to perform the operation in-memory, which is usually  
slower). Unfortunately, we'll probably also throw an exception when  
you try to actually execute a subselect against the database.



On Mar 17, 2007, at 6:19 AM, Dave wrote:

> On 3/16/07, Marc Prud'hommeaux <mprudhom@apache.org> wrote:
>> This does look like a bug in MySQL (see http://bugs.mysql.com/ 
>> bug.php?
>> id=5037 ). Supposedly this is fixed in as of version 5.0.20.
>
> Thanks for looking into this.
>
> I'm using 5.0.27-standard, so perhaps that bug is not the problem --
> or it wasn't fixed.
>
>
>> In general, we use subselects for bulk operations because delete and
>> update SQL statements do not allow the specification of multiple
>> tables, so only the simplest bulk operations would be possible
>> without the ability to use subselects.
>
> Is it possible to turn off OpenJPA generated sub-selects and only do a
> sub-select when an application query uses one? That's the default
> behavior in Toplink/JPA.
>
> - Dave


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