Re: PL/Python: How do I use result methods?

On Sat, Oct 16, 2004 at 03:34:29PM +0100, Oliver Elphick wrote:
>
> According to the docs (8.0):
>
> Calling plpy.execute with a query string and an optional limit
> argument causes that query to be run and the result to be
> returned in a result object. The result object emulates a list
> or dictionary object. The result object can be accessed by row
> number and column name. It has these additional methods: nrows
> which returns the number of rows returned by the query, and
> status which is the SPI_execute() return value.
>
> What exactly is the syntax for using the nrows and status methods?
>
> I am trying to use it like this:
>
> ...
> arec = plpy.execute(plan, [ addrno ], 1)
> plpy.info("Executed plan")
> n = plpy.nrows(arec)

The documentation describes nrows as being a method of the result
object, so I'd guess it should be used thusly:

n = arec.nrows()

I tried that with the following function:

CREATE OR REPLACE FUNCTION test() RETURNS INTEGER AS $$
rv = plpy.execute('SELECT usename FROM pg_user')
n = rv.nrows()
return 1
$$ LANGUAGE plpythonu;

The function failed:

test=> SELECT test();
ERROR: plpython: function "test" failed
DETAIL: exceptions.SystemError: error return without exception set

Digging through plpython.c I discovered the following:

#ifdef NOT_USED
/* Appear to be unused */
static PyMethodDef PLy_result_methods[] = {
{"fetch", (PyCFunction) PLy_result_fetch, METH_VARARGS, NULL,},
{"nrows", (PyCFunction) PLy_result_nrows, METH_VARARGS, NULL},
{"status", (PyCFunction) PLy_result_status, METH_VARARGS, NULL},
{NULL, NULL, 0, NULL}
};
#endif

It looks like nrows(), status(), and fetch() aren't available as
result object methods. I don't know what would happen if you
un-#ifdef-ed that block and the two others that are related;
perhaps one of the developers can tell us what's going on.

If the methods aren't available then they probably shouldn't be
mentioned in the doc.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/