Alvaro Herrera <alvherre@commandprompt.com> writes:
> To be honest, I panicked for a second when I saw the new
> SnapshotResetXmin call, before I realized that it wasn't necessary
> before. The serializable case makes more sense the patched way, I
> think.
Yeah, in the old coding, SnapshotResetXmin would have happened
implicitly at the last UnregisterSnapshot call. In this arrangement,
the "last UnregisterSnapshot" is going to be the manual one in
AtEOXact_Snapshot, so we need a manual SnapshotResetXmin there too.
I chose to put it at the bottom of the routine so that it's guaranteed
to fire even if the RegisteredSnapshots count was corrupted, but that's
just paranoia.
regards, tom lane
