| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | Neil Conway <neilc(at)samurai(dot)com>, Christopher Browne <cbbrowne(at)acm(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Seqscan in MAX(index_column) |
| Date: | 2003-09-05 03:32:24 |
| Message-ID: | 27375.1062732744@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Tom Lane wrote:
>> You could doubtless maintain a fairly good approximate total this
>> way, and that would be highly useful for some applications ...
>> but it isn't COUNT(*).
> With MVCC allowing multiple rows with only one visible, I thought the
> INSERT/DELETE system would work --- once the delete becomes visible, the
> change becomes visible.
Oh, you're imagining the cache as being a row in an ordinary table?
I doubt that could work. Multiple transactions trying to update these
rows would suffer from contention and deadlock problems, wouldn't they?
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Christopher Browne | 2003-09-05 03:44:31 | Re: Seqscan in MAX(index_column) |
| Previous Message | Ben Grimm | 2003-09-05 03:31:50 | Re: pg_dump/all doesn't output schemas correctly (v7.3.4) |