Обсуждение: Re: Index Backward Scan fast / Index Scan slow ! (Modifié par Pailloncy Jean-Gérard)

Hi,

> In 7.4 a VACUUM should be sufficient ... or at least, if it isn't
Atfer VACUUM:
dps=# explain analyze select next_index_time from url order by
next_index_time desc limit 1;

QUERY PLAN
------------------------------------------------------------------------
------------------------------------------------------------------------
--
  Limit  (cost=0.00..2.62 rows=1 width=4) (actual time=0.098..0.099
rows=1 loops=1)
    ->  Index Scan Backward using url_next_index_time on url
(cost=0.00..814591.03 rows=310913 width=4) (actual time=0.096..0.096
rows=1 loops=1)
  Total runtime: 0.195 ms
(3 rows)

dps=# explain analyze select next_index_time from url order by
next_index_time asc limit 1;

QUERY PLAN
------------------------------------------------------------------------
------------------------------------------------------------------------
-
  Limit  (cost=0.00..2.62 rows=1 width=4) (actual
time=13504.105..13504.106 rows=1 loops=1)
    ->  Index Scan using url_next_index_time on url
(cost=0.00..814591.03 rows=310913 width=4) (actual
time=13504.099..13504.099 rows=1 loops=1)
  Total runtime: 13504.158 ms
(3 rows)

Better, but......

Cordialement,
Jean-Gérard Pailloncy

=?ISO-8859-1?Q?Pailloncy_Jean-G=E9rard?= <pailloncy@ifrance.com> writes:
>> In 7.4 a VACUUM should be sufficient ... or at least, if it isn't
> Atfer VACUUM:
> Better, but......

... but not much :-(.  Okay, could we see VACUUM VERBOSE results for
this table?

            regards, tom lane