Re: Index Backward Scan fast / Index Scan slow !

[ Ah, I just got to your message with the VACUUM VERBOSE results ... ]

=?ISO-8859-1?Q?Pailloncy_Jean-G=E9rard?= <pailloncy@ifrance.com> writes:
> dps=# VACUUM VERBOSE url;
> INFO:  index "url_next_index_time" now contains 349519 row versions in
> 3534 pages
> DETAIL:  229515 index row versions were removed.
> 3071 index pages have been deleted, 2864 are currently reusable.
> CPU 0.32s/0.67u sec elapsed 76.25 sec.

Hm, this is odd.  That says you've got 349519 live index entries in only
463 actively-used index pages, or an average of 754 per page, which
AFAICS could not fit in an 8K page.  Are you using a nondefault value of
BLCKSZ?  If so what?

If you *are* using default BLCKSZ then this index must be corrupt, and
what you probably need to do is REINDEX it.  But before you do that,
could you send me a copy of the index file?

            regards, tom lane