On 2012-12-18 19:56:18 -0500, Robert Haas wrote: > On Tue, Dec 18, 2012 at 5:25 PM, anara...@anarazel.de > <and...@anarazel.de> wrote: > > The problem is that at the time GetSnapshotData returns the xmin horizon > > might have gone upwards and tuples required for decoding might get removed > > by other backends. That needs to be prevented while holding the procarray > > lock exclusively. > > Well, for the ordinary use of GetSnapshotData(), that doesn't matter, > because GetSnapshotData() also updates proc->xmin. If you're trying > to store a different value in that field then of course it matters.
Absolutely right. I don't want to say there's anything wrong with it right now. The "problem" for me is that it sets proc->xmin to the newest value it can while I want/need the oldest valid value... I will go with adding a already_locked parameter to GetOldestXmin then. Thanks for the input, Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
