Re: HeapTupleSatisfiesToast() busted? (was atomic pin/unpin causing errors)

Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Tue, May 10, 2016 at 12:19 PM, Andres Freund <andres@anarazel.de> wrote:
> >> It's not super likely, yea. But you don't really need to "use" 4 billion
> >> oids to get a wraparound. Once you have a significant number of values
> >> in various toast tables, the oid counter progresses really rather fast,
> >> without many writes. That's because the oid counter is global, but each
> >> individual toast write (and other things), perform checks via
> >> GetNewOidWithIndex().
> 
> > Understood.
> 
> Sooner or later we are going to need to go to 8-byte TOAST object
> identifiers.  Maybe we should think about doing that sooner not later
> rather than trying to invent some anti-wraparound solution here.

Umm, it seems to me like we need this fixed in supported branches, not
just 9.7, so I don't think 8-byte toast IDs are a reasonable solution at
this point.

> In principle, you could support existing TOAST tables and pointers
> containing 4-byte IDs in parallel with the new ones.  Not sure how
> pg_upgrade would handle it exactly though.

I suppose the real problem is that there's no way to have a mix of 4-
and 8-byte identifiers in the same toast table.  I suppose we could have
two toast tables for each regular table, but that sounds pretty painful.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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