From a python module, called from a pl/python function, how to get the return value?

Question

Is there any reason this function call would not return 'result'?

CREATE OR REPLACE FUNCTION myfunction (input int, OUT result int) AS $$

result = mymodule.object(input,plpy)
plpy.info(" ========= EXTRA-module result: ===",result)

$$ LANGUAGE plpythonu;

=== Content of mymodule ============

def object(input,plpy):
  import StringIO
  try:
   plan = plpy.prepare("INSERT INTO file VALUES (nextval('primary_sequence'),$1) RETURNING primary_key", ["integer"] )
  except:
   plpy.error(traceback.format_exc())

  try:
   rv = plpy.execute(plan, [ input ])
   result = rv[0]["primary_key"]
   plpy.info(" ========= INTRA-module result: ===",result)
   return result
  except:
   plpy.error(traceback.format_exc())

what do you mean by noresult no INTRA-module result or no EXTRA-module result ? — Xavier Combelle, Sep 21 '11 at 16:56
@ed.,@Xavier: BOTH of the info calls show the correct result! It's just the 'return' itself which doesn't seem to work as expected. I want the 'wrapping' function to return result - pls note its OUT parameter. — DrLou, Sep 21 '11 at 18:45
Does it work if you use the RETURNS syntax instead of OUT? (I.e. ...myfunction (input int) RETURNS int) AS $$). You'll need a return statement after the "EXTRA-module" .info() call... — ed., Sep 21 '11 at 18:59

score 1 · Answer 1 · answered Sep 21 '11 at 17:17

1

I'm not to familiar with plpython, but if it is throwing an error and that isn't getting printed out or passed further up the chain you would never know.

I don't know if you are testing with a command line or not but try putting a print statement in your except blocks to see if it is just erroring out instead of returning.

answered Sep 21 '11 at 17:17

Prodigal Maestro

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That's a problem in plpy - cannot print as such. But do have the plpy.info call to effect the same purpose. It's the poor man's debugger! – DrLou Sep 21 '11 at 18:47

score 1 · Accepted Answer · answered Sep 22 '11 at 12:26

@ed. Didn't actually need the RETURNS syntax instead of OUT, but your suggestion put me onto the answer. And yes, I feel like a real dummy. This is the beauty of having others review one's work.

with the return result added, things work out nicely. Key assumption I'd made here was that the result = syntax did not actually finish the return within the scope of the calling function. Doh!

CREATE OR REPLACE FUNCTION myfunction (input int, OUT result int) AS $$

result = mymodule.object(input,plpy)
plpy.info(" ========= EXTRA-module result: ===",result)
# This was the key bit:
return result

$$ LANGUAGE plpythonu;

From a python module, called from a pl/python function, how to get the return value?

2 Answers2