The Python code you write gets transformed into a function. E.g.,
CREATE FUNCTION myfunc(text) RETURNS text
AS 'return args[0]'
LANGUAGE 'plpython';
gets transformed into
def __plpython_procedure_myfunc_23456():
return args[0]
where 23456 is the OID of the function.
If you do not provide a return value, Python returns the default
None which may or may not be what you want. The
language module translates Python's None into the
SQL null value.
The PostgreSQL function parameters are available in
the global args list. In the
myfunc example, args[0] contains
whatever was passed in as the text argument. For
myfunc2(text, integer), args[0]
would contain the text variable and
args[1] the integer variable.
The global dictionary SD is available to store
data between function calls. This variable is private static data.
The global dictionary GD is public data,
available to all Python functions within a session. Use with care.
Each function gets its own restricted execution object in the
Python interpreter, so that global data and function arguments from
myfunc are not available to
myfunc2. The exception is the data in the
GD dictionary, as mentioned above.
