Does getting the primary keys via the Statement.getGeneratedKeys()
require an extra round-trip to the database? If not, I would think it
wouldn't generate very much overhead, since I'm already sending a
statement to the database, and receiving a response. Otherwise, yes, I
can definitely see how it would be more efficient to batch primary keys.
Questions about Cayenne's primary key batching: Is this done globally,
across contexts? Or would each DataContext instance manage its own batch
of keys to use?
Thanks,
Shea.
Interestingly, using autoincrement in mysql is probably a /hit/ in
performance, compared to the default strategy. Cayenne has to ask
mysql what the id was after every insert.
In the default PK generation scheme, cayenne manages the ids. Hence,
cayenne can batch ids and not have to talk to the db about every pk
for every object.
Robert
On Oct 21, 2008, at 10/219:12 AM , Michael Shea wrote:
Hi Andrus,
Thanks for your reply... Of course, this is almost exactly what
Cayenne is for. I erred in the question I was asking, unfortunately,
so I will ask it properly this time... =). I really just have a minor
question to ask:
My two database schemas are *almost* identical, but not quite. The
MySQL database creates primary keys on certain tables by using an
AUTOINCREMENT column. The Oracle database creates primary keys on the
equivalent tables by using a custom sequence. Is there any way for me
to change the primary key generation strategy depending on which DBMS
is in use? Or will I have to choose a strategy that works equally on
both Oracle and on MySQL (ie, switch to using the default strategy?).
I would ideally like to continue using the auto-increment columns on
MySQL, since that intuitively seems like the most efficient method to
me. I have experimented with customizing the mapping.xml file at
runtime based on which type of database I'll be using, before making
any calls to cayenne, that seems to work. But it's also pretty hacky,
and will make maintenance more painful.
Thanks,
Mike Shea.
Hi Michael,
Cayenne will detect the database type automatically on startup and
use the right adapter. So yes, use JNDI to abstract connection
information, beyond that no need for any extra tricks. You generic
Cayenne mapping will just work regardless of the db type.
Andrus
On Oct 20, 2008, at 11:42 AM, Michael Shea wrote:
Hi guys,
I am working on a project in which I have to support multiple
database types. They do not have to be supported simultaneously - I
need my program to be able to run whether I am using an Oracle
database or a MySQL database (the databases will have the same
schema), but the database type does not change at runtime.
I am wondering if there are any best practices or recommendations
for how to approach this problem. Currently, I am planning on
simply creating two sets of cayenne configuration files in
different directories (ie, a map.xml and a cayenne.xml file), and
just adding one or the other of these directories to the classpath,
depending on some initial configuration parameters that tell me
what type of database I'm accessing. The datasource is defined via
JNDI.
Does anyone think that this is a good idea or a bad idea, or have a
better way of doing this? =) I am using Cayenne 2.0.4.
Thanks!
Mike Shea.
