Re: Problem with planner - Mailing list pgsql-general

Try to change index: objects_endings_tsz_active(state,endings_tsz)
where state='active'.

2011/8/8, hubert depesz lubaczewski <depesz@depesz.com>:
> Hi,
> we have 8.3.11 installation on client site, with table, which looks like
> this:
>
> $ \d objects
>                                               Table "public.objects"
>          Column          |           Type           |
>    Modifiers
> -------------------------+--------------------------+---------------------------------------------------------------
> ...
>  state                   | text                     |
> ...
>  ending_tsz              | timestamp with time zone | default (now() + '4
> mons'::interval)
> ...
> Indexes:
>     "objects_stat_user_id_creation_tsz" btree (state, user_id, creation_tsz)
>     "objects_ending_tsz_active" btree (ending_tsz) WHERE state =
> 'active'::text
>     "objects_ending_tsz_idx" btree (ending_tsz)
> ...
>
>
> and we have a query:
> select count(*) from objects where state='active'::text and ending_tsz <= (
> select now() - '1 day'::interval );
>
> Normally this query has been getting plan, using
> objects_ending_tsz_active, which is sane and fast.
>
> But today, without any sensible reason, it switched to:
>
>                                                        QUERY PLAN
>
>
-------------------------------------------------------------------------------------------------------------------------
>  Aggregate  (cost=6719810.62..6719810.63 rows=1 width=0)
>    InitPlan
>      ->  Result  (cost=0.00..0.01 rows=1 width=0)
>    ->  Bitmap Heap Scan on objects  (cost=1289719.58..6711422.56
> rows=3355219 width=0)
>          Recheck Cond: ((state = 'active'::text) AND (ending_tsz <= $0))
>          ->  BitmapAnd  (cost=1289719.58..1289719.58 rows=3355219 width=0)
>                ->  Bitmap Index Scan on objects_stat_user_id_creation_tsz
> (cost=0.00..334318.95 rows=10065657 width=0)
>                      Index Cond: (state = 'active'::text)
>                ->  Bitmap Index Scan on objects_ending_tsz_idx
> (cost=0.00..953722.77 rows=24986738 width=0)
>                      Index Cond: (ending_tsz <= $0)
> (10 rows)
>
> running analyze objects 2 times in a row fixed the issue, but hour later
> - the problem came back.
>
> what can be wrong?
>
> Best regards,
>
> depesz
>
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>
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--
------------
pasman