Hi
We are using orientDB in a webapp that uses a REST api combined with
Orients Java Object api.
We will almost exclusively only need transaction when updating an object
but currently we do not
track the version in REST api. The latest update call for a certain object
is thus considered the latest version.
The problem is that an update to one object might affect another, thus we
need transactions, preferably optimistic ones.
We don't entirely understand the documentation but our basic approach have
been:
for (int i = 0; i < TRANSACTION_RETRY_COUNT; i++) {
try {
db.getTransaction().begin();
doStuff(userUpdatedObject);
tempObject = db.save(userUpdatedObject);
db.getTransaction().commit();
userUpdatedObject= tempObject ;
break;
} catch (OConcurrentModificationException e) {
if (i == TRANSACTION_RETRY_COUNT - 1) {
throw e;
}
}
}
That is, the userUpdatedObject is not tracked by the db. It comes from the
REST api and doesn't have any version.
- When is the OConcurrentModificationException? I am assuming in the
commit function?
- We get a OConcurrentModificationException. We catch the exception and
retry, how does the begin() function know that the previous transaction was
aborted and it should start a new one and not a nested transaction?
- Do we need to do a rollback after we caught the
OConcurrentModificationException? Or is that already done when the
exception is thrown? Basically, when do we need to manually rollback?
- What would happen if, for example, doStuff() throw another type of
exception, AnotherException, that we also catch. Will it be a nested
transaction then?
- If so, do we need to do a rollback after we catch
AnotherException?
- What is the difference between db.getTransaction().begin() and
db.begin()? With the later one I can choose transaction strategy (except
only optimistic is supported). Which one should we be using?
Overall, is this the correct approach or how should one go about it? Thanks
for all the help!
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