Re: row-attribute in EXPLAIN-output doesn't match count(*)

Andrew Sullivan <ajs(at)crankycanuck(dot)ca> writes:

> On Thu, Apr 14, 2005 at 07:21:38PM +0200, Andreas Joseph Krogh wrote:
> >
> > So, what you're suggesting is that a restart of the webapp should make vacuum
> > able to delete those dead rows?
>
> Yes, but that'll only solve your problem for now. You'll have the
> problem again soon. What's keeping open the transaction?

This is presumably because of the long-standing issue that Postgres takes the
snapshot as soon as the BEGIN is issued. A lot of drivers issue a "COMMIT;
BEGIN;" right away even though it could be a long time before any actual work
is done.

Other databases (by which I mean Oracle) treat BEGIN as a noop. The snapshot
starts when the first SQL statement that needs a snapshot is executed. So
until a SELECT is issued the connection doesn't participate in any
transactional issues like keeping old versions of records around.

--
greg