On Fri, Oct 24, 2014 at 2:12 PM, Florian Pflug <f...@phlo.org> wrote: >> What about doing one scan using SnapshotAny and then testing each >> returned row for visibility under both relevant snapshots? See >> whether there is any tuple for which they disagree. > > See my other mail - testing whether the snapshots agree isn't enough, > you'd have to check whether there could have been *any* snapshot taken > between the two which would see a different result.
Oh, hmm. I had thought what I was proposing was strong enough to handle that case, but now I see that it isn't. However, I'm not entirely sure that it's the RI code's job to prevent such cases, or at least not when the transaction isolation level is less than serializable. Is there an argument that the anomaly that results is unacceptable at REPEATABLE READ? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
