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From "Philip Copeland" <>
Subject Transactions , Primary Keys
Date Sat, 22 Sep 2007 22:26:45 GMT


We've used Cayenne extensively over the last 2 years - with great
success on many projects. 


I'm in the process of designing & implementing a generic import/export
feature for some of our projects - and its raising some difficult issues
that I don't know how to resolve. We're currently using the 1.2 code
base and generally use the database generated Primary Key option. The
import/export raise challenges because its potentially dealing with very
large amounts of data - and the hard part is that I need to "remap" the
foreign key relationships as part of the process. We've though of
several ways of doing this but they all involve being able to query
objects that have not yet been written to the database. At the same time
the import needs to happen as a "transaction" so that it can be rolled
back if something fails.


The main problem I'm facing is that objects don't get written to the
database (nor Primary Keys generated) unless we commit our transaction.
What I'm wishing for is a mode where all changes are made to the
underlying database - but not committed until I have completed all the
work I need to do. The central issue is that I need to be able to
perform database queries on objects that are uncommitted (and part of my
current transaction) - and I don't have a way to do this at present with
Cayenne. The though of having to go back to JDBC for this is not


The more I think about this - the more I wonder why the "write or save"
function is not handled separately from a "commit". 


I'd be very interested if anyone has suggestions.






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