| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Dylan Hansen <dhansen(at)pixpo(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net> |
| Subject: | Re: auto-vacuum & Negative "anl" Values |
| Date: | 2006-06-22 18:40:13 |
| Message-ID: | 2266.1151001613@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Dylan Hansen <dhansen(at)pixpo(dot)com> writes:
> I have been spending some time looking into how auto-vacuum is
> performing on one of our servers. After putting the PostgreSQL logs
> in debug I noticed that the threshold for ANALYZE was never being hit
> for a particular table because the calculated value becomes
> increasingly negative.
Hmm, it shouldn't ever be negative at all, I would think. The
calculation in question is
anltuples = tabentry->n_live_tuples + tabentry->n_dead_tuples -
tabentry->last_anl_tuples;
Apparently somehow last_anl_tuples has managed to get to be bigger than
n_live_tuples, which maybe could happen after a delete. Should we be
clamping last_anl_tuples to not exceed n_live_tuples somewhere?
Alvaro and Matthew, what do you think?
regards, tom lane
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