Neil Conway wrote:
On Tue, 2008-03-25 at 17:26 -0300, Alvaro Herrera wrote:
There is one hole here: contention on ProcArrayLock. Basically, for
simple transactions we will need to update MyProc after every command.
If we're just updating MyProc->xmin, we only need to acquire
ProcArrayLock in shared mode, right?
In fact, do you need a lock at all? We already assume that
reading/writing a TransactionId is atomic in many places. We acquire
ProcArrayLock at the end of transaction when we clear MyProc->xid, to
ensure that we don't exit the set of running transactions while someone
else is taking a snapshot, but AFAICS that's not necessary when we just
advance MyProc->xmin.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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