Re: Index Backward Scan fast / Index Scan slow !

=?ISO-8859-1?Q?Pailloncy_Jean-G=E9rard?= <pailloncy@ifrance.com> writes:
> How to optimize the last query ? (~ 2000 times slower than the first
> one)
> I suppose there is some odd distribution of data in the index ?

Looks to me like a whole lot of dead rows at the left end of the index.
Have you VACUUMed this table lately?  It would be interesting to see
what VACUUM VERBOSE has to say about it.

> Is the solution to reindex data ?

In 7.4 a VACUUM should be sufficient ... or at least, if it isn't
I'd like to know why not before you destroy the evidence by reindexing.

            regards, tom lane