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Re: [postgis-users] Error with "return query" ( "return next" working ) with custom type - Mailing list pgsql-general

From Rémi Cura
Subject Re: [postgis-users] Error with "return query" ( "return next" working ) with custom type
Date
Msg-id CAJvUf_viMR8N5L1OPFfs4zw9r+is=dDkzYtD-UAUiOPEATBNWA@mail.gmail.com
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In response to Re: [postgis-users] Error with "return query" ( "return next" working ) with custom type  (Steve Grey <steven.c.r.grey@gmail.com>)
Responses Re: [postgis-users] Error with "return query" ( "return next" working ) with custom type
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Hey,
thanks for the answers,

sorry for the cross post, i didn't know if it was postgis or postgres issue, hence the double post (removed postgis now).

I'm afraid I don't understand perfectly the answer. Are you (both) saying that it is a normal behavior that a function that should return a custom type doesn't in fact return this custom type, but a number of columns composing this custom type?

This seems like at best a strange behavior !

The whole point of using custom type is to provide interface, right? 

To be precise, when specifying "return setof fake_topogeometry" I would expect that the function returns a  fake_topogeometry object (like the querry `SELECT (5,5,5,5)::fake_topogeometry`), not some columns !

I'm obviously missing something, as
SELECT * FROM testTopogeom(); --returns columns
SELECT testTopogeom(); --returns object

Could you suggest me some more documentation (other than http://www.postgresql.org/docs/9.3/static/plpgsql-control-structures.html)?

Is this difference between Return Next and return query documented?

Thanks for your help,
Cheers,
Rémi-C


2013/10/23 Steve Grey <steven.c.r.grey@gmail.com>
try:

RETURN QUERY  SELECT 1,1,1,1;

The error message means the cast failed between ttt.fake_topogeometry and the topology_id (i.e. first) field of the return type of the function, which isn't what you wanted to do.

Pls. don't cross-post between lists.


On 23 October 2013 01:21, Rémi Cura <remi.cura@gmail.com> wrote:


Hey dear lists,

Here is a self contained example showing strange behavior from a real life example concerning the use of postgis_topology topogeometry type.


The problem is :
when trying to return setof topogeometry,
the "return query"  gives an error of type where there is none, and the return next is working fine.

The precise error message is ERROR 42804
"ERROR:  structure of query does not match function result type
DETAIL:  Returned type ttt.fake_topogeometry does not match expected type integer in column 1.
CONTEXT:  PL/pgSQL function ttt.testtopogeom(ttt.fake_topogeometry) line 9 at RETURN QUERY
"

Is it ok, postres bug, postgis bug?
What are the possible corrections?


Here is the self contained code stored in the "ttt" schema.

DROP SCHEMA IF EXISTS ttt CASCADE;
CREATE SCHEMA ttt;

DROP TYPE IF EXISTS ttt.fake_topogeometry CASCADE;
CREATE TYPE ttt.fake_topogeometry AS
   (topology_id integer,
    layer_id integer,
    id integer,
    a_type integer);

DROP FUNCTION IF EXISTS ttt.testTopogeom(test_topom ttt.fake_topogeometry);
CREATE FUNCTION ttt.testTopogeom(test_topom ttt.fake_topogeometry)
RETURNS SETOF ttt.fake_topogeometry AS
$BODY$
-- this function is an empty function to test return of multiple topogeom
DECLARE
the_topo ttt.fake_topogeometry;
BEGIN
RETURN NEXT (1,1,1,1)::ttt.fake_topogeometry;
--RETURN NEXT (3,3,3,3)::ttt.fake_topogeometry;

RETURN QUERY  SELECT (1,1,1,1)::ttt.fake_topogeometry as foo;
-- UNION 
--SELECT  (3,3,3,3)::ttt.fake_topogeometry as foo
RETURN  ;
END ;
$BODY$
LANGUAGE plpgsql IMMUTABLE;

SELECT *
FROM ttt.testTopogeom((2,2,2,2)::ttt.fake_topogeometry);


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