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I am running the below query and try to identify the end point of a line with gid 338 on the polygon's boundary with gid 1456 but got some error message:

SELECT public.st_contains((Select public.st_EndPoint(the_geom) from lines where gid=338),(select public.st_Boundary(the_geom) from polygons where gid=1456))

The error message:

> ERROR:  function _st_contains(public.geometry, public.geometry) does
> not exist LINE 1: SELECT $1 && $2 AND _ST_Contains($1,$2)
> HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
> QUERY:  SELECT $1 && $2 AND _ST_Contains($1,$2) CONTEXT:  SQL function
> "st_contains" during inlining

If I run

SELECT ST_Contains(ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'),ST_GeomFromText('point(3 3)'));

It will return "t" as the correct value.

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The function is ST_Contains(), you can't call it using lower case letters e.g. st_contains as far as I know. –  Nathan W Oct 29 '13 at 5:18
    
Upper or lower case in function names doesn't matter in PostgreSQL –  Nicklas Avén Oct 29 '13 at 7:03
    
I solved the problem by using select _st_contains(...) instead of select st_contains(...). According to the manual " This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Contains." –  Xianlin Oct 29 '13 at 7:50
    
@NicklasAvén there you go didn't know that. Been using SQL Server which seems to care. –  Nathan W Oct 29 '13 at 10:01
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1 Answer 1

up vote 3 down vote accepted

Edited

Take a look at the doc: http://postgis.net/docs/manual-2.1/ST_Contains.html

Sorry, I misread your question first.

Interesting that it didn't work with your first syntax but with _st_contains().

But the way you do it is not the way you usually do it in SQL.

Your query will run with indexes if you rewrite to something like:

SELECT public.st_contains(st_EndPoint(lines.the_geom), st_Boundary(polygons.the_geom))
FROM lines, polygons 
WHERE lines.gid=338 and polygons.gid=1456;

May I guess that what you want is tho find all cases where the lines endpoints is on the boundary of a polygon. That you do with something like:

SELECT lines.gid, polygon.gid 
FROM lines INNER JOIN polygons 
ON ST_Contains(st_EndPoint(lines.the_geom), ST_Bounadary(polygons.the_geom));
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I used your new format with "inner join" and I am able to find those lines endpoints is on the boundary of a polygon. Thanks! –  Xianlin Oct 30 '13 at 2:26
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