On Wed, Jul 20, 2016 at 7:57 AM, Andres Freund <and...@anarazel.de> wrote: > > > On July 19, 2016 7:14:42 PM PDT, Amit Kapila <amit.kapil...@gmail.com> wrote: >>On Wed, Jul 20, 2016 at 5:02 AM, Andres Freund <and...@anarazel.de> >>wrote: >>> On 2016-07-19 18:09:59 -0500, Kevin Grittner wrote: >>>> As far as I can see, to do this the way that Andres and Amit >>>> suggest involves tying in to indexam.c and other code in incredibly >>>> ugly ways. >>> >>> Could you explain the problem you're seing? >>> >>> Isn't pretty much all all that we need to do: >>> 1) add a InitSnapshotToast(Snapshot originMVCCSnap), which sets >>SnapshotData->lsn >>> to the the origin snapshot's lsn >>> 2) adapt TestForOldSnapshot() to accept both HeapTupleSatisfiesMVCC >>and >>> HeapTupleSatisfiesToast? >>> >> >>I also think so. However, it is not clear what is the best place to >>initialize toast snapshot. One idea could be to do it in >>GetSnapshotData() after capturing the required information for the >>valid value of old_snapshot_threshold. Do you have something else in >>mind? > > There's very few callsites using toast snapshots. I'd just do it there. Don't > think we ever use GetSnapshotData for them. >
I think Snapshot's members whenTaken and lsn are updated/initialized only in GetSnapshotData(). So if GetSnapshotData() is not used, how will you expect those fields to be updated. We need those fields to be updated for TestForOldSnapshot(). -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
