Re: Getting return value from .callproc

On 06/28/2016 12:05 AM, Larry Sevilla wrote:
> My background is MS SQL and VB.
>
> I'm new to Postgresql, Python & psycopg2.
>
>
> I have a problem in getting return value from a UDF in PostgreSQL into
> Python.
>
> using PGAdmin3.
>
> table created:
> -----
> CREATE TABLE public.personnel
> (
> companyid integer NOT NULL,
> fullname character varying(100) NOT NULL,
> ts timestamp without time zone NOT NULL,
> serialid smallint NOT NULL DEFAULT
> nextval('personnel_serialid_seq'::regclass),
> CONSTRAINT personnel_pkey PRIMARY KEY (serialid),
> CONSTRAINT personnel_companyid_key UNIQUE (companyid),
> CONSTRAINT personnel_fullname_key UNIQUE (fullname)
> )
> WITH (
> OIDS=FALSE
> );
> ALTER TABLE public.personnel
> OWNER TO postgres;
> -----
>
> UDF to insert data and return the serialid:
> -----
> CREATE OR REPLACE FUNCTION public.personnelinsert(
> incompanyid integer,
> infullname character varying)
> RETURNS integer AS
> $BODY$
> DECLARE
> retval integer;
> BEGIN
> INSERT INTO personnel
> (
> companyid ,
> fullname ,
> ts
> )
> VALUES
> (
> incompanyid ,
> infullname ,
> now()
> )
> RETURNING serialid INTO retval;
> RETURN retval;
> END;
> $BODY$
> LANGUAGE plpgsql VOLATILE
> COST 100;
> ALTER FUNCTION public.personnelinsert(integer, character varying)
> OWNER TO postgres;
> -----
>
>
> using PGAdmin's query:
> -----
> select personnelinsert(12345,'Newton, Isaac');
> -----
> I got personnelinsert = 1 (ok)
>
>
> using "sudo -u postgres psql postgres"
> -----
> select personnelinsert(23456,'Einstein, Albert');
> -----
> I got personnelinsert = 2 (ok)

Why are you running psql via sudo? You should only need to run "psql postgres".

>
>
> But if I use Python with psycopg2
> -----
> import psycopg2
>
> conn=psycopg2.connect(host='localhost',database='postgres',user='postgres',password='postgres')
> cur=conn.cursor()
>
> retval = cur.callproc('personnelinsert',[34567,'Galilei, Galileo'])
>
> conn.commit()
>
> cur.close()
> conn.close()
>
> print(retval)
> -----
> retval = [34567,'Galilei, Galileo']
> (I'm expecting retval/serialid value of 3, not the parameters I sent)
>
>
> Q1: From Python, is there a way I can retrieve the value of
> "retval/serialid" of my UDF?

Return values from Postgres functions are just like other expression values. The most straightforward way to retrieve your function's return value would be something like this:

cur.execute('select personnelinsert(%s, %s)',[34567,'Galilei, Galileo'])
retval = cur.fetchone()[0]

Read the manual for more about retrieval methods:
http://initd.org/psycopg/docs/cursor.html#fetch

>
> Q2: I'm trying the OUT parameter, but cannot figure out. How can I
> access the OUT parameter from Python?

I've never messed with OUT parameters or callproc, but the manual seems pretty clear:

http://initd.org/psycopg/docs/cursor.html?highlight=callproc#cursor.callproc

--
Jonathan Rogers
Socialserve.com by Emphasys Software
jrogers(at)emphasys-software(dot)com