I wrote:
> "Peter Brant" <Peter.Brant@wicourts.gov> writes:
>> Does that also explain why an attempt to make a new connection just
>> hangs?
> Actually, I was just wondering about that --- seems like a bare
> connection attempt should not generate any WAL entries. Do you have any
> nondefault actions in ~/.psqlrc or something like that?
I just repeated the hangup scenario here, and confirmed that I can still
start and stop a plain-vanilla psql session (no ~/.psqlrc, no special
per-user or per-database settings) without it hanging. I can also do
simple read-only SELECTs. So I'm thinking your hang must involve some
additional non-read-only actions.
[ thinks for awhile longer ... ] No, I take that back. Once you'd
exhausted the current pg_clog page (32K transactions), even read-only
transactions would be blocked by the need to create a new pg_clog page
(which is a WAL-logged action). A read-only transaction never actually
makes a WAL entry, but it does still consume an XID and hence a slot on
the current pg_clog page. So I just hadn't tried enough transactions.
regards, tom lane