I have following table and data.
create table test ( id bigserial not null,
geo geometry not null );
insert
into
test(geo)
values ('MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))'),
('POLYGON ((0 0, 5 0, 5 5, 0 5, 0 0))'),
('POLYGON ((2 2, 5 2, 5 5, 2 5, 2 2))');
select * from test;
id|geo |
--|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
5|MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))|
6|POLYGON ((0 0, 5 0, 5 5, 0 5, 0 0)) |
7|POLYGON ((2 2, 5 2, 5 5, 2 5, 2 2)) |
following query (Q) should return all rows
select
*
from
test t
where
st_contains('MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))',
geo);
id|geo |
--|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
5|MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))|
6|POLYGON ((0 0, 5 0, 5 5, 0 5, 0 0)) |
Because following constraint returns true.
select
st_contains('MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))',
'POLYGON ((2 2, 5 2, 5 5, 2 5, 2 2))');
What is wrong here with the query Q above?
The input geometry is invalid, and so is the result as per the doc:
So ST_Contains(A,B) implies ST_Within(B,A) except in the case of invalid geometries where the result is always false regardless or not defined.
WITH test(geo) as (
values ('MULTIPOLYGON (((0 0, 0 0, 0 7, 0 7, 0 0)), ((0 0, 0 7, 7 7, 7 0, 0 0)), ((0 0, 7 0, 7 0, 0 0, 0 0)), ((7 7, 7 7, 7 0, 7 0, 7 7)), ((0 7, 0 7, 7 7, 7 7, 0 7)), ((0 0, 7 0, 7 7, 0 7, 0 0)))'),
('POLYGON ((0 0, 5 0, 5 5, 0 5, 0 0))'),
('POLYGON ((2 2, 5 2, 5 5, 2 5, 2 2))'))
select st_isvalid(geo), st_isvalidreason(geo) from test;
st_isvalid | st_isvalidreason
------------+-------------------------------------------
f | Too few points in geometry component[0 7]
t | Valid Geometry
t | Valid Geometry
That being said, you may want to read carefully the doc on st_contains and st_covers as there are subtleties when the geometries share an edge.