Andres Freund <andres@2ndquadrant.com> wrote:
> We can play cute tricks akin to what CREATE INDEX CONCURRENTLY currently
> does, i.e. wait for all other relations that could have possibly seen
> the old relfilenode (they must have at least a share lock on the
> relation) before dropping the actual storage.
>
> The reason we cannot currently do that in most scenarios is that we
> cannot perform transactional/mvcc updates of non-exclusively locked
> objects due to the SnapshotNow problems of seeing multiple or no
> versions of a row during a single scan.
Not only would that be slower than the submitted patch in cases
where only a few rows differ, but it could be waiting to swap in
that new heap for an unbounded amount of time. I think the current
patch will "play nicer" with incremental maintenance than what you
suggest here.
--
Kevin Grittner
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
