On July 19, 2016 7:43:05 PM PDT, Amit Kapila <amit.kapil...@gmail.com> wrote: >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().
That's why I suggested copying them from the current mvcc snapshot. Andres -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
