| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Glen Parker" <glenebob(at)nwlink(dot)com> |
| Cc: | "Pg-General" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Screwy Statistics... |
| Date: | 2002-09-09 18:45:28 |
| Message-ID: | 12610.1031597128@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
"Glen Parker" <glenebob(at)nwlink(dot)com> writes:
> First, shouldn't statistics have some clue how many rows might be in the
> table, at least right after an analyze?
Only approximately -- VACUUM or VACUUM ANALYZE will generate an
exact-as-of-the-moment reltuples entry, but just ANALYZE doesn't,
because it doesn't do a complete table scan.
We have an open bug report about ANALYZE's guesstimate sometimes being
further off than one would like. This happens because it estimates
the entire file's tuples-per-page fill factor from that of the first
few pages, and of course that could be radically wrong.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2002-09-09 19:01:51 | Re: Unable to locate type name '? in catalog ERROR |
| Previous Message | Larry Rosenman | 2002-09-09 18:26:21 | Re: pg_restore not able to restore files larger that 2.4GB |