Thread: How can I retrieve a function result?
Hi pgsql community,
I'm using libpq C. I'm trying to execute a FUNCTION called "myFunction",
*********************************************************************************************************
PGResult *res;
res = PQexecParams ( conn, "select myFunction($1,$2,$3)" , 3, NULL, paramValues, paraLenghts, paramFormats, resultFormat);
if ( PQresultStatus (res) != PGRES_TUPLES_OK)
{
//error
}else{
//ok
}
*********************************************************************************************************
It's works fine, however I dont know how can I retrieve the result that return the FUNCTION "myFunction". "myFunction" is a postgres FUNCTION which returns a INT.
Any advices??
thanks in advance.
Luis.
--
paz, amor y comprensión
(1967-1994)
Luis, On Mon, Jun 12, 2006 at 06:24:24PM -0500, Luis Alberto Pérez Paz wrote: > res = PQexecParams ( conn, "select myFunction($1,$2,$3)" , 3, NULL, > paramValues, paraLenghts, paramFormats, resultFormat); > It's works fine, however I dont know how can I retrieve the result that > return the FUNCTION "myFunction". "myFunction" is a postgres FUNCTION which > returns a INT. libpq functions for retrieving query results are described here: http://www.postgresql.org/docs/8.1/static/libpq-exec.html#LIBPQ-EXEC-SELECT-INFO Have you tried them and do you have a special problem with one of those? If so, please give more detail. Getting the result of a function does not differ from getting the result of a regular select of a table or view. Joachim
Hi,
Thanks a lot for your answer,
Let me give you a simple example with more detail:
In my postgres database I have a function called "myFunction".
/************************************************************************/
CREATE OR REPLACE FUNCTION myFunction(INT) RETURN INT AS '
DECLARE
indice ALIAS FOR $1;
BEGIN
IF indice > 0 THEN
return -900;
ELSE
//something to do....
return 0;
END IF;
END;
' LANGUAGE 'plpgsql';
/************************************************************************/
I have a program in C/C++ which call the FUNCTION 'myFunction'
/************************************************************************/
res = PQexecParams ( conn, "select myFunction($1)" , 1, NULL,
paramValues, paraLenghts, paramFormats, resultFormat);
/************************************************************************/
paramValues, paraLenghts, paramFormats, resultFormat);
/************************************************************************/
The program works fine, actually I can verify that it executes the FUNCTION 'myFunction', however I dont know how can I get the return value of the FUNCTION 'myFunction' (as you can see in the little example the return value can be 0 or -900).
Regards,
Thanks in advance!
On 6/12/06, Joachim Wieland <joe@mcknight.de> wrote:
Luis,
On Mon, Jun 12, 2006 at 06:24:24PM -0500, Luis Alberto Pérez Paz wrote:
> res = PQexecParams ( conn, "select myFunction($1,$2,$3)" , 3, NULL,
> paramValues, paraLenghts, paramFormats, resultFormat);
> It's works fine, however I dont know how can I retrieve the result that
> return the FUNCTION "myFunction". "myFunction" is a postgres FUNCTION which
> returns a INT.
libpq functions for retrieving query results are described here:
http://www.postgresql.org/docs/8.1/static/libpq-exec.html#LIBPQ-EXEC-SELECT-INFO
Have you tried them and do you have a special problem with one of those? If
so, please give more detail.
Getting the result of a function does not differ from getting the result of
a regular select of a table or view.
Joachim
--
paz, amor y comprensión
(1967-1994)
Luis,
On Tue, Jun 13, 2006 at 01:19:32PM -0500, Luis Alberto Pérez Paz wrote:
> The program works fine, actually I can verify that it executes the FUNCTION
> 'myFunction', however I dont know how can I get the return value of the
> FUNCTION 'myFunction' (as you can see in the little example the return
> value can be 0 or -900).
this is similar to retrieving the result of a query that returned one row
and one column. So you just have to use PQgetvalue(res, 0, 0).
Here are a few other examples:
Check if there were rows at all:
if (PQntuples(res) == 0) {
/* no rows */
PQclear(res);
return (char*) 0;
}
Check if there was anything else than one column per row:
if (PQnfields(res) != 1) {
/* did not get only 1 column back */
PQclear(res);
return (char*) 0;
}
Check whether or not the first column, first row field is NULL:
if (PQgetisnull(res, 0, 0)) {
/* got NULL */
PQclear(res);
return (char*) 0;
}
Get the first row, first column value as char*:
db_value = PQgetvalue(res, 0, 0);
I hope this gives you an idea.
Those functions are in this section of the documentation:
http://www.postgresql.org/docs/8.1/static/libpq-exec.html#LIBPQ-EXEC-SELECT-INFO
Joachim
Thank you Joachim,
it woks!
Regards,
Luis A Perez Paz
On 6/13/06, Joachim Wieland <joe@mcknight.de> wrote:
Luis,
On Tue, Jun 13, 2006 at 01:19:32PM -0500, Luis Alberto Pérez Paz wrote:
> The program works fine, actually I can verify that it executes the FUNCTION
> 'myFunction', however I dont know how can I get the return value of the
> FUNCTION 'myFunction' (as you can see in the little example the return
> value can be 0 or -900).
this is similar to retrieving the result of a query that returned one row
and one column. So you just have to use PQgetvalue(res, 0, 0).
Here are a few other examples:
Check if there were rows at all:
if (PQntuples(res) == 0) {
/* no rows */
PQclear(res);
return (char*) 0;
}
Check if there was anything else than one column per row:
if (PQnfields(res) != 1) {
/* did not get only 1 column back */
PQclear(res);
return (char*) 0;
}
Check whether or not the first column, first row field is NULL:
if (PQgetisnull(res, 0, 0)) {
/* got NULL */
PQclear(res);
return (char*) 0;
}
Get the first row, first column value as char*:
db_value = PQgetvalue(res, 0, 0);
I hope this gives you an idea.
Those functions are in this section of the documentation:
http://www.postgresql.org/docs/8.1/static/libpq-exec.html#LIBPQ-EXEC-SELECT-INFO
Joachim
--
paz, amor y comprensión
(1967-1994)