On Wed, Jun 9, 2010 at 12:35 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Simon Riggs <si...@2ndquadrant.com> writes: >> On Tue, 2010-06-08 at 18:03 -0400, Robert Haas wrote: >>> OK, yes, I see what you're getting at now. There are two possible >>> ways to do freeze the tuples and keep the xmin: we can either rely on >>> the PD_ALL_VISIBLE page-level bit (as I previously proposed) or we can >>> additionally have a HEAP_XMIN_FROZEN bit as you propose here. I am >>> not sure which way is better. > >> Doing it at tuple level is more flexible and allows more aggressive >> freezing. It also works better with existing tuple visibility code. > > I agree, relying on a page-level bit (or field) is unpleasant in a > number of ways. > > But none of this accomplishes a damn thing towards the original goal, > which was to avoid an extra disk write associated with freezing (not > to mention an extra write for setting the transaction-committed hint > bit). Setting a bit is no cheaper from that standpoint than changing > the xmin field. >
Could a tuple wih the bit set be considered frozen already? Would we actually ever need to rewrite the xmin, even for anti-wraparound reasons? Greetings Marcin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
