Re: ATTACH/DETACH PARTITION CONCURRENTLY

On Thu, Jan 31, 2019 at 1:02 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> New patch series attached.

And here's yet another new patch series, rebased over today's commit
and with a couple of other fixes:

1. I realized that the PartitionDirectory for the planner ought to be
attached to the PlannerGlobal, not the PlannerInfo; we don't want to
create more than one partition directory per query planning cycle, and
we do want our notion of the PartitionDesc for a given relation to be
stable between the outer query and any subqueries.

2. I discovered - via CLOBBER_CACHE_ALWAYS testing - that the
PartitionDirectory has to hold a reference count on the relcache
entry. In hindsight, this should have been obvious: the planner keeps
the locks when it closes a relation and later reopens it, but it
doesn't keep the relation open, which is what prevents recycling of
the old PartitionDesc. Unfortunately these additional reference count
manipulations are probably not free. I don't know expensive they are,
though; maybe it's not too bad.

Aside from these problems, I think I have spotted a subtle problem in
0001. I'll think about that some more and post another update.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company