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From Andrus Adamchik <>
Subject Re: How to propoerly close context db connection
Date Tue, 01 Apr 2008 08:47:26 GMT
Hi Colin,

Cayenne internal cache state is in no way related to the connection  
state - it can survive closing connections, etc. If you are connecting  
to a separate DB process, Cayenne cache management techniques (as  
mentioned by Marcin, and what you found in the docs), is the only  
thing you need to know.

Embedded DB's add a whole other dimension to that by keeping committed  
data in memory at the driver level - something Cayenne is not aware  
of. So anything you do with "clearCache" or RefreshQuery, etc.,  
affects Cayenne cache, and not the embedded DB JDBC layer. So here  
you'd need to read the embedded DB docs (is that Derby, HSQL, H2?) and  
see what they recommend to do in such situation. There maybe a SQL  
query that would shutdown/reopen the file, or something else (like  
restarting the DataSource).


On Apr 1, 2008, at 4:13 AM, Colin Bankier wrote:
> Thanks Andrus - but shouldn't something like getQueryCache().clear()  
> at least
> clear any cache so that cayenne will retrieve the data fresh from  
> the DB
> once the file has been overwritten? (Even if the connection isn't  
> closed
> properly while this is happening.) This doesn't seem to be having any
> effect.
> I've also tried to look at the CAY-632 RefreshQuery, or
> context.invalidateObjects(), but really wanted to refresh the whole  
> cache -
> not just a particular collection of objects. Perhaps I just need to  
> know how
> to use these correctly.
> Any suggestions on how to do this would be greatly appreciated.
> Cheers,
> Colin.
> Andrus Adamchik wrote:
>> Cayenne itself works with a DataSource. All connection management and
>> starting and stopping the embedded DB is deferred to the DataSource
>> and is beyond Cayenne scope. The default DataSource implementation
>> pools connections. If you need a different policy, you need to  
>> provide
>> a DataSource that does whatever is appropriate in your environment.
>> Custom DataSource is installed by providing a special
>> DataSourceFactory for a give DataNode in the Modeler.
>> Andrus
> -- 
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