Re: Incorrect visibility test function assigned to snapshot

Bruce Momjian <bruce@momjian.us> wrote:

> On Wed, May 30, 2018 at 09:28:54AM -0400, Alvaro Herrera wrote:
> > On 2018-May-30, Antonin Houska wrote:
> > 
> > > In the header comment, SnapBuildInitialSnapshot() claims to set
> > > snapshot->satisfies to the HeapTupleSatisfiesMVCC test function, and indeed it
> > > converts the "xid" array to match its semantics (i.e. the xid items eventually
> > > represent running transactions as opposed to the committed ones). However the
> > > test function remains HeapTupleSatisfiesHistoricMVCC as set by
> > > SnapBuildBuildSnapshot().
> > 
> > Interesting.  While this sounds like an oversight that should have
> > horrible consequences, it's seems not to because the current callers
> > don't seem to care about the ->satisfies function.  Are you able to come
> > up with some scenario in which it causes an actual problem?
> 
> Uh, are we going to fix this anyway?  Seems we should.

Sorry, I forgot. Patch is below and I'm going to add an entry to the next CF.

-- 
Antonin Houska
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26, A-2700 Wiener Neustadt
Web: https://www.cybertec-postgresql.com