[postgis-users] Strange result about spatial indexes?

[Paul Ramsey]

That link isn't downloading for me, it's an HTML page instead of a tar file...

On Thu, Aug 13, 2009 at 9:03 PM, Jose Carlos<jomarlla at cgf.upv.es> wrote:
> Hi,
> I made the table smaller for sharing. Now the table has just 1600 rows.
> The effect still remains.  I tried with others tables and other PostGIS
> versions, I tried even just with tables with POINT features getting similar
> results.
>
> Thanx,
> Best
>
> You can download the table from here:
> http://cid-40b8dee7bf5b661f.skydrive.live.com/self.aspx/.Public/data.tgz
>
> test3=# explain analyze select count(*) from suelos1 s1, suelos1 s2
> where (s1.geom && s2.geom);
>                                                                QUERY
> PLAN
> -------------------------------------------------------------------------------------------------------------------------------------------
>  Aggregate  (cost=1095.91..1095.92 rows=1 width=0) (actual
> time=2840.187..2840.189 rows=1 loops=1)
>   ->  Nested Loop  (cost=0.00..1079.87 rows=6416 width=0) (actual
> time=0.111..2820.408 rows=13808 loops=1)
>         ->  Seq Scan on suelos1 s1  (cost=0.00..130.04 rows=1604
> width=4597) (actual time=0.009..2.580 rows=1604 loops=1)
>         ->  Index Scan using suelos1_geom on suelos1 s2
> (cost=0.00..0.58 rows=1 width=4597) (actual time=0.778..1.729 rows=9
> loops=1604)
>               Index Cond: (s1.geom && s2.geom)
>  Total runtime: 2840.270 ms
> (6 rows)
>
> test3=# explain analyze select count(*) from suelos1 s1, suelos1 s2
> where (st_expand(s1.geom,00) && s2.geom);
>                                                                QUERY
> PLAN
> -------------------------------------------------------------------------------------------------------------------------------------------
>  Aggregate  (cost=1087.92..1087.93 rows=1 width=0) (actual
> time=212.789..212.790 rows=1 loops=1)
>   ->  Nested Loop  (cost=0.00..1087.89 rows=13 width=0) (actual
> time=0.090..189.842 rows=13808 loops=1)
>         ->  Seq Scan on suelos1 s1  (cost=0.00..130.04 rows=1604
> width=4597) (actual time=0.012..2.632 rows=1604 loops=1)
>         ->  Index Scan using suelos1_geom on suelos1 s2
> (cost=0.00..0.58 rows=1 width=4597) (actual time=0.043..0.084 rows=9
> loops=1604)
>               Index Cond: (st_expand(s1.geom, 0::double precision) &&
> s2.geom)
>  Total runtime: 212.864 ms
>
>
> (6 rows)
>
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