Andres Freund <and...@2ndquadrant.com> wrote: > Kevin Grittner <kgri...@ymail.com> wrote:
>>> Alexander Korotkov <aekorot...@gmail.com> wrote: >>> >>>> Could we start snapshot-importing transaction with repeatable >>>> read isolation level? >> If you are talking about having pg_dump acquire a safe snapshot and >> have cooperating processes in the same pg_dump run use that >> snapshot in repeatable read transactions, then yes -- that would >> work. As long as a repeatable read transaction is using a safe >> snapshot it will not see any anomalies. > Why could it be unsafe to import a snapshot that's been generated as > serializable deferrable into another backend? That wouldn't be unsafe, which is what I was saying the post you responded to. > Doesn't the fact that it > has been exported out of a deferrable xact that's still running pretty > much guarantee that the other xact is also safe? As long as it is at least repeatable read, yes. > ISTM that the check is just overzelous and/or needs to be moved into > ImportSnapshot(). There it then could be made to check if the exporting > xact was also deferrable. That would be great if ImportSnapshot had access to that information; I don't see it, though. Having pg_dump use repeatable read transactions for the processes that import the snapshot would work fine, as long as they are reading a snapshot which was captured by a serializable read only deferrable transaction. -- Kevin Grittner EDB: 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
