Re: adding import in pl/python function - Mailing list pgsql-hackers

On Fri, May 24, 2013 at 4:22 PM, Szymon Guz <mabewlun@gmail.com> wrote:
> Hm... maybe you're right. I think I don't understand fully how the
> procedures are executed, and I need to read more to get it.

Well, it's easy.

Instead of PLyFloat_FromNumeric[0], you can make a
PLyDecimal_FromNumeric. There, you'd do with the Python/C[1]:

PyObject *decimal = PyImport_Import("decimal");
PyObject *decimal_dict = PyModule_GetDict(decimal);
PyObject *decimal_ctor = PyDict_GetItemString(decimal_dict, "Decimal");

And invoke it with a string rep of your Numeric:

PyObject *value = PyObject_CallFunction(decimal_ctor, "S", string_value);

Add of course all kinds of error checking and reference count boiler
plate, and you'd have a very dumb version of it.

To make it more "pro", you'd want to do all that stuff to get
decimal_ctor only at initialization time. Especially since you don't
want to fumble with the import lock right there in _FromNumeric.

And to make it totally "pro", you can even freeze Decimal (using
pyfreeze) if you'd like. I would only do this in contexts where you
don't have a stdlib of course. Not sure whether windows falls into
that category. Linux doesn't.


[0] http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/pl/plpython/plpy_typeio.c#l518
[1] http://docs.python.org/2/c-api/import.html