[postgis-users] Problem using set-returning functions

[Markus Schaber]

Hi,

I'm cross-posting this to the plpgsql list:

We've run into a small problem creating a set-returning function for
PostGIS in PostgreSQL 8.1.0:

CREATE OR REPLACE FUNCTION generate_x (geom geometry)
RETURNS SETOF double precision AS
'DECLARE
    index integer;
BEGIN
    FOR index IN 1 .. npoints(geom) LOOP
	RETURN NEXT X(geometryn(geom,index));
    END LOOP;
END
' LANGUAGE 'plpgsql' IMMUTABLE STRICT;

Now, trying to use this function yields the following error:

navteq=# select foo,generate_x(bar) from test;
ERROR:  set-valued function called in context that cannot accept a set
CONTEXT:  PL/pgSQL function "generate_x" line 5 at return next

However, it is fine to call other set returning functions in the same
context:

navteq=# select foo,dump(bar) from test;
 foo |                       dump
-----+--------------------------------------------------
  42 | ({1},0101000000000000000000F03F0000000000000040)
  42 | ({2},010100000000000000000008400000000000001040)
  42 | ({3},010100000000000000000014400000000000001840)
  23 | ({1},01010000000000000000001C400000000000002040)
(4 rows)

navteq=# select foo,x(geometryn(bar,generate_series(1,npoints(bar))))
FROM test;
 foo | x
-----+---
  42 | 1
  42 | 3
  42 | 5
  23 | 7
(4 rows)

(This third query is equal to what I expected the failing query to do.)

The table "test" looks as follows;

navteq=# \d test
      Table "public.test"
 Column |   Type   | Modifiers
--------+----------+-----------
 foo    | integer  |
 bar    | geometry |

navteq=# select foo,asText(bar) from test;
 foo |         astext
-----+-------------------------
  42 | MULTIPOINT(1 2,3 4,5 6)
  23 | MULTIPOINT(7 8)
(2 rows)


I'm shure its a small detail I've blindly ignored, but I'm stuck ATM.



Thanks,
Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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