[postgis-users] Strange result about spatial indexes?

[Paul Ramsey]

No surprise, any function that returns cheaply and immutably will
provide the same effect. The effect is so huge, that you can even get
faster results using expensive functions.

suelos=# select count(*) from suelos1 p1, suelos1 p2 where
(st_envelope(p1.geom) && p2.geom);
 count
-------
 13808
(1 row)
Time: 92.989 ms

suelos=# select count(*) from suelos1 p1, suelos1 p2 where
(st_setsrid(p1.geom,23030) && p2.geom);
 count
-------
 13808
(1 row)
Time: 92.626 ms

suelos=# select count(*) from suelos1 p1, suelos1 p2 where
(st_convexhull(p1.geom) && p2.geom); count
-------
 13808
(1 row)
Time: 237.928 ms

suelos=# select count(*) from suelos1 p1, suelos1 p2 where (p1.geom && p2.geom);
 count
-------
 13808
(1 row)
Time: 478.765 ms