On Thu, Apr 16, 2015 at 2:23 AM, Andres Freund <and...@anarazel.de> wrote: > I'm, completely independent of logical decoding, of the *VERY* strong > opinion that 'speculative insertions' should never be visible when > looking with normal snapshots. For one it allows to simplify > considerations around wraparound (which has proven to be a very good > idea, c.f. multixacts + vacuum causing data corruption years after it > was thought to be harmless). For another it allows to reclaim/redefine > the bit after a database restart/upgrade. Given how complex this is and > how scarce flags are that seems like a really good property. > > And avoiding those flags to be visible to the outside requires a WAL > record, otherwise it won't be correct on the standby.
I'm a bit distracted here, and not sure exactly what you mean. What's a normal snapshot? Do you just mean that you think that speculative insertions should be explicitly affirmed by a second record (making it not a speculative tuple, but rather, a fully fledged tuple)? IOW, an MVCC snapshot has no chance of seeing a tuple until it was affirmed by a second in-place modification, regardless of tuple xmin xact commit status? -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
