Andres Freund <and...@2ndquadrant.com> wrote: > On 2015-01-28 15:32:15 +0000, Kevin Grittner wrote: >> Andres Freund <and...@2ndquadrant.com> wrote: >>> 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. > > Then add that information? The disk format for snapshot isn't persistent > across restarts, so we can just extend it. > > I really don't like adding hacks like using a lower serializability > level than what's actually requested just because it happens to be > easier. Even if it's just in some backend.
I see your point, and will look at that for the master branch, but it hardly seems like something to back-patch; and the messy failure of this combination of options on 9.3 and 9.4 seems like it deserves a fix. Tom Lane <t...@sss.pgh.pa.us> wrote: > Kevin Grittner <kgri...@ymail.com> writes: >> >> Kevin Grittner <kgri...@ymail.com> wrote: >>> 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. >> >> It looks like the attached patch does it (although it is only >> lightly tested so far and only on the master branch). This seems >> like a back-patchable bug fix (to 9.3). >> >> Thoughts? > > A comment seems essential here, because as written anybody would think > the test for a snapshot is a bug. Good point. -- 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