On 6/02/12 9:48 AM, Daniel Scheibe wrote:
It's causing me an out of memory / permgen space exception since (from what i
can tell) Cayenne is keeping all the records im memory until the
commitChanges() call.
Am 05.02.2012 23:32, schrieb Aristedes Maniatis:
On 6/02/12 7:26 AM, Daniel Scheibe wrote:
Thanks Ari,
i'm trying to store information about the content of archives (ZIP and
RAR) inside a database table. They usually consist of a few hundred up
to 20-30k thousand entries and i would like to keep this inside a
transaction either suceeding or failing in a whole for a single
archive. Of course i could issue commits in between and process them
in chunks but its more work and harder to maintain the rollback of the
process if something goes wrong or fails during the import phase. As
previously mentioned i have it working with plain SQL statements but
would love to integrate Cayenne in between to get the full advantage
and convenience of an O/R mapper. Furthermore i'm using XADisk's
support for transactions on the filesystem level to keep it
synchronized with the database (also works out great with larger
transactions).
Appreciating your help! I will search the list again, maybe i've
missed some stuff that has been discussed already.
Cheers,
Daniel
Am 05.02.2012 13:28, schrieb Aristedes Maniatis:
On 5/02/12 10:11 PM, Daniel Scheibe wrote:
Hi guys,
i'm trying to figure out how Cayenne is handling transactions in
regards of when data is transferred to the database. I am trying to
get some large transactions (many small records or a few very large
records) working and so far haven't had luck. If i understand
correcly, Cayenne is holding my records in a cache and when i execute
the commitChanges() on the ObjectContext it starts to transfer all of
the data to the database (isolated in a real database transaction). So
my question is (and please correct me if my previuos assumption is
wrong) how can I influence on this behaviour since i pretty much need
Cayenne to use the database transaction more directly. When i skip
Cayenne and issue SQL statements right through the JDBC connection
(ie.g. BEGIN TRANSACTION, UPDATE, UPDATE, UPDATE..., COMMIT
TRANSACTION) it works fine as with MySQL i'm only restricted to the
maximum allowed size of the InnoDB transaction logfile which is quite
sufficient for my purposes. On the other hand
i
completely understand that Cayenne would not know when i've finished
working with an Entity as there is no kind of "save" command on the
Entity itself.
Oh, this of course only goes for storing data inside the database, not
for reading.
Maybe some of you guys with a bit more insight into the Cayenne
internals can help me out on this or point me to the right direction.
Thanks in advance and a refreshing weekend!
Cheers,
Daniel
Can you explain a little more what you are trying to do and what problem
you are trying to avoid. Yes, there are ways to control the transactions
through Cayenne (search this list for many previous thread discussing
this), but it sounds like you just need to commit your context at the
appropriate places in your code.
Ari
OK, good. Then what is the problem with using a single commit for the
whole batch?
Ari
Daniel,
Why do you post at the top of the emails when I've replied to the bottom?
Now that we actually know what your problem is that you are trying to solve,
perhaps someone can help. I believe the only approach is to take control of the
transactions yourself in order to be able to bypass the normal behaviour of
Cayenne with regard to committing and wrapping several commits in one
transaction. Then you can break up the Cayenne commits into smaller chunks and
wrap the whole thing in a database transaction you manage yourself. I've never
needed to do that myself, but I believe it is possible.
They usually consist of a few hundred up to 20-30k thousand entries
If that means 20,000-30,000 entries, and the objects aren't too big, you should
be able to commit that in one go with a bit more RAM (yes, Cayenne will keep
the objects in memory). If you mean 20,000-30,000 thousand entries (that is,
20-30 million) then I think you are out of the realm where an ORM is a good
solution for your problem.
Ari
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Aristedes Maniatis
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