On 10/10/07, Marko Kreen <[EMAIL PROTECTED]> wrote: > On 10/10/07, Tom Lane <[EMAIL PROTECTED]> wrote: > > * Why is txid_current_snapshot() excluding subtransaction XIDs? That > > might be all right for the current uses in Slony/Skytools, but it seems > > darn close to a bug for any other use. > > In queue usage the transaction that stores snapshots does not do > any other work on its own, so it does not matter, main requirement > is that txid_current()/txid_current_snapshot() be symmetric - > whatever the txid_current() outputs, the txid_current_snapshot() measures. > > But I agree, supporting subtransactions makes the API more > universal. And it wouldn't break Slony/PgQ current usage.
I thought about it with a clear head, and am now on optinion that the subtransactions should be left out from current API. I really fail to imagine a scenario where it would be useful. The module main use comes from the scenario where txid_current(), txid_current_snapshot() and reader of them are all different transactions. Main guarantee that the APi makes is that as soon you can see a inserted snapshot in table, you can also see all inserted events in different table. There does not seem to be any use of them intra-transaction. Adding them currently in would be just premature bloat. We can do it always later, when someone presents a case for them. Then we can also decide whether it should be added to current API or have parallel API besides. It should not break Slony/Skytools either way. -- marko ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
