On Fri, Jun 11, 2004 at 09:27:07AM +0100, Richard Huxton wrote: > >If the transaction is rolled back, the local state variable is > >thrown away. If the transaction is commited and the local state > >variable has been invalidated then the global state variable is > >invalidated, otherwise the global state variable is updated using > >a a state merge function, specific to the aggregate. > > Isn't this going to have visibility issues wrt other backends? How do I > know what transactions have updated the global and what haven't and > which I should currently be seeing?
The global is only updated at transaction commit. So, if you take a local snapshot of the global at the beginning of your transaction then the visible changes at any point are those from transactions that commited before your transaction started. That's well-defined, at least, and appears to be pretty much the same as the standard read commited isolation level. > I'm not sure that there is a solution simpler than the "insert +1/-1 > into summary table" that gets discussed. That's fairly slow and painful. Cheers, Steve ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
