Tom Lane wrote on 27.12.2011 20:22:
If I'm understanding you correctly, you could just make it check the
transaction status.  If there's an active transaction, then there are
"uncommitted changes".

Sounds like what I want, but how do I check the "transaction status" (I'm using 
JDBC)

More specifically, look to see if the current transaction has assigned
itself a transaction ID.  I think the easiest place to see this is in
pg_locks --- it will be holding exclusive lock on a TransactionId object
if so.

There are various cases where you could get a false positive from this
type of test, eg if a subtransaction made some changes and then rolled
back, you'll have an XID even though there's not really anything to
commit.  But it will never give a false negative.

                        regards, tom lane


Thanks for the answer. I came up with the following statement:

select count(*)
from pg_locks
where pid = pg_backend_pid()
and locktype in ('transactionid')

does that look right to you?

If the count is > 0 then I have uncommitted changes

Regards
Thomas




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