Re: Planner issue

Alex Turner wrote:

>I get the following output from explain analyze on a certain subset of
>a large query I'm doing.
>
>
>
Try increases the statistics on the listprice column with alter
table and then re-run analyze.

alter table foo alter column set statistics <n>

Sincerely,

Joshua D. Drake


>From the looks of it, I need to increase how often postgres uses an
>index over a seq scan, but I'm not sure how to do that.  I looked
>through the run-time configuration docs on the website, but didn't see
>anything pertaining to index selectivity.
>
>Thanks,
>
>Alex Turner
>netEconomist
>
>
>trendmls=# explain analyze select listnum from propmain where
>listprice<=300000 and listprice>=220000;
>                                                  QUERY PLAN
>--------------------------------------------------------------------------------------------------------------
> Seq Scan on propmain  (cost=0.00..15556.05 rows=6228 width=4) (actual
>time=0.093..506.730 rows=5671 loops=1)
>   Filter: ((listprice <= 300000::numeric) AND (listprice >= 220000::numeric))
> Total runtime: 510.482 ms
>(3 rows)
>
>trendmls=# explain analyze select listnum from propmain where
>listprice<=300000 and listprice>=250000;
>                                                                QUERY PLAN

>------------------------------------------------------------------------------------------------------------------------------------------
> Index Scan using propmain_listprice_i on propmain
>(cost=0.00..12578.65 rows=3486 width=4) (actual time=0.103..16.418
>rows=3440 loops=1)
>   Index Cond: ((listprice <= 300000::numeric) AND (listprice >=
>250000::numeric))
> Total runtime: 18.528 ms
>(3 rows)
>
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