On Wed, Jul 27, 2022 at 5:56 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Maybe we need a different function for pg_visibility to call?
> If we want ComputeXidHorizons to serve both these purposes, then it
> has to always deliver exactly the right answer, which seems like
> a definition that will be hard and expensive to achieve.
Yeah, I was thinking along similar lines.
I'm also kind of wondering why these calculations use
latestCompletedXid. Is that something we do solely to reduce locking?
The XIDs of running transactions matter, and their snapshots matter,
and the XIDs that could start running in the future matter, but I
don't know why it matters what the latest completed XID is.
--
Robert Haas
EDB: http://www.enterprisedb.com