Re: Transaction completion timing

"Steve Dodd" <steve@streetcontxt.com> writes:
> Say we have two transactions run sequentially: T1 writes some data, and T2 reads the written data. There is a
non-zerotime delay between the apparent T1 commit, and the subsequent T2 query. 
> Is there any guarantee that the data written in T1 will be visible to the query in T2?

> We have a situation in our system where it would appear that the answer is NO.

Extremely hard to believe.  There is a very well-defined point where the
transaction's effects become visible to other transactions, and that is
certainly before the commit is reported as complete to the client.
I suspect if you dig into it you'll find that your client-side code
is doing something unexpected.

Also worth checking is that "T2" is actually a transaction, and not
a single statement within a serializable-mode transaction.  In the latter
case it would see the database state as of the transaction's snapshot,
which might precede T1's commit.

            regards, tom lane