NpgsqlCommand.DeriveParametersForFunction

I’m trying to integrate Npgsql to EntLib here https://github.com/Chavoshi/EnterpriseLibrary.NetCore/pull/27 and EntLib tries to match the number of parameter provided by the user with the number of the parameters detected on the database.

Looks like the query used at NpgsqlCommand.DeriveParametersForFunction is not returning good results for functions that RETURNS SETOF table.

The code is creating one output parameter for each column on the table due to the following code:

                    if (names != null && i < names.Length)
                        param.ParameterName = names[i];
                    else
                        param.ParameterName = "parameter" + (i + 1);

Example function:

CREATE OR REPLACE FUNCTION public.obtercamera(
	pcameraid integer)
    RETURNS SETOF camera 
    LANGUAGE 'plpgsql'

    COST 100
    VOLATILE 
    ROWS 1000
AS $BODY$

BEGIN

	RETURN QUERY
	SELECT CameraId, CameraUrl, Ativo, Criacao, Atualizacao 
	FROM Camera 
	WHERE CameraId = pCameraId OR pCameraId IS NULL;
					  
END

$BODY$;

[jrocha]

Got it. Since DAAB is no longer under active development I think the way I managed this behavior to work both ways in DAAB adapter is the best approach.

Nevertheless, IMHO, I don’t think the way Npgsql does it today is semantically consistent. If in the future PostgreSQL starts to support IN, OUT and RETURNS SETOF record (like obtercamera2) it would became confusing.

– Edit: obtercamera2 signature works.

[Brar]

Ok, thank you.

So what I meant to say was that the following 3 function signatures are functionally equivalent in PostgreSQL and Npgsql:

CREATE FUNCTION obtercamera1(cameraid integer) RETURNS SETOF camera AS ...;

CREATE FUNCTION obtercamera2(
	INOUT cameraid integer,
	OUT cameraurl character varying(255),
	OUT ativo boolean,
	OUT criacao timestamp without time zone,
	OUT alteracao timestamp without time zone
) RETURNS SETOF record AS ...;

CREATE FUNCTION obtercamera3(cameraid integer) RETURNS TABLE(
    cameraid integer,
    cameraurl character varying(255),
    ativo boolean,
    criacao timestamp without time zone,
    alteracao timestamp without time zone
) AS ...;

Edit: edited demo signatures after thinking twice what the correct signature would have to look like.

All 3 signatures should (I haven’t actually tested it today) return the same result set in PostgreSQL and derive the same one IN and 4 5 OUT parameters in Npgsql.

I understand that this isn’t what the Entlib DAAB is expecting but that’s how it is currently implemented.

Changing this would certainly need a broader discussion as it is a change that will break some peoples’ code. Especially given the fact that Entlib is no longer under active development.

From a purity point of view I’d support the argument that obtercamera1 and obtercamera3 can bee seen as different from obtercamera2 from the frontends perspective and shouldn’t derive any OUT parameters.

cc: @roji @austindrenski @YohDeadfall