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
exceptionset
 

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/