On Tue, Apr 10, 2018 at 7:24 PM, Pavan Deolasee <pavan.deola...@gmail.com> wrote:
> Hi Heikki, > > On Tue, Apr 10, 2018 at 7:07 PM, Heikki Linnakangas <hlinn...@iki.fi> > wrote: > >> >>> >> It would seem more straightforward to add a snapshot parameter to >> GetNewOidWithIndex(), so that the this one caller could pass SnapshotToast, >> while others pass SnapshotDirty. With your patch, you check the index >> twice: first with SnapshotDirty, in GetNewOidWithIndex(), and then with >> SnapshotToast, in the caller. >> > > Hmm. I actually wrote my first patch exactly like that. I am trying to > remember why I discarded that approach. Was that to do with the fact that > SnapshotToast > can't see all toast tuples either? Yeah, I think so. For example, it won't > see tuples with uncommitted-xmin, leading to different issues. Now it's > unlikely that we will have a OID conflict where the old tuple has > uncommitted-xmin, but not sure if we can completely rule that out. > Or may be we simply err on the side of caution and scan the toast table with SnapshotAny while looking for a duplicate? That might prevent us from reusing an OID for a known-dead tuple, but should save us a second index scan and still work. Thanks, Pavan -- Pavan Deolasee http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
