Re: BUG #17949: Adding an index introduces serialisation anomalies. - Mailing list pgsql-bugs

On Mon, Jun 19, 2023 at 2:29 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> S2:  _bt_search(&buf)

> S1:  INSERT ...

> S2:    PredicateLockRelation(...);

> My point is that S2 won't ever scan S1's tuples, so it won't pass S1's
> xid to CheckForSerializableConflictOut()

[completing that sentence a little more] ... so this was our only
chance to detect that S2 read an object that S1 wrote.  But the
_bt_search() and PredicateLockXXX() calls are not atomic and not
rechecked, so a write between them is invisible to the algorithm.  I'm
not sure about this, but it's the idea I'm exploring...