Simon Riggs wrote: > On Sun, 2004-04-25 at 19:06, Alvaro Herrera wrote: > > Hackers, > > > > This patch adds subtransaction support into the storage manager. Files > > created or dropped inside a subtransaction are correctly dealt with at > > subtransaction commit or abort. > > > - pg_clog/pg_subtrans. Need a solution. > > > > > > PS: somehow I managed to get tired of the phrase "nested transactions" > > and I'm using the term "subtransactions" instead. In my head they are > > the same thing ... > > Impressive. > > As you're aware, our current work overlaps. > pg_clog doesn't seem like the place to record subtransactions, though > maybe it is... could we not give subtransactions a txnid just as with > flat transactions? That way we can record everything in pg_clog AND > recovery will work without further modification - as long as the failure > of a top level transaction causes failure of every subtransaction EVEN > if the subtrans originally committed.
The problem is we have to atomically mark multiple transactions as committed/aborted in pg_clog. Each subtransaction does get its own xid, it is just that pg_subtrans maps each xid to is parent xid for use in atomically marking the xids as committed/aborted. Recovery via xlog should be fine. > If you add pg_subtrans, you will need to make recovery work all over > again...really, you don't want to be doing that, do you? > > I also have other questions.... > Forgive my lack of attention: I want SAVEPOINTs, not subtransactions... > how do we do those? Savepoints are basically just a BEGIN at the save point, and a ROLLBACK to get you back to the saved spot. It is just window-dressing on top of nested transactions. > My last focus on this was to do with SQL handling of transactional > rollback characteristics on error. PostgreSQL performs rollback on > complete txn when error occurs, rather than allowing statement level > abort and then retry...this was characterised as requiring "nested > transactions"...are your aware of this...is it on your roadmap. Yes, that is the whole point --- to allow individual queries to fail without rolling back the entire transaction. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
