问题
For some reason, passing a string from Python into a Postgres function and calling it using a psycopg2 cursor causes the function to be unrecognized because the argument is unknown.
The function is very simple like so:
CREATE OR REPLACE FUNCTION text_test (some_text text)
RETURNS void AS $$
BEGIN
END;
$$ LANGUAGE plpgsql;
On the python side, I have:
cursor.callproc("text_test", ("test",))
And I get the following error:
psycopg2.ProgrammingError: function text_test(unknown) does not exist
LINE 1: SELECT * FROM text_test('test')
^
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Why does this only happen with strings and what do I need to do to have a function successfully accept a string? For some reason numeric data types are unaffected by this problem.
回答1:
This happens because there is no way to cast the string to the "correct" text type. Is it a char(N)? A varchar(N)? A text?
Unfortunately .callproc() doesn't provide an easy way to specify the argument types but you can always use .execute() casting the arguments explicitly and everything works:
curs.execute("SELECT * FROM text_test(%s::text)", ("test",))
回答2:
You could also make a list with the parameters you need to send:
param_list = ["test"]
curs.callproc(proc_name, param_list)
Here is a good answer about it: python + psycopg2 = unknown types?
来源：https://stackoverflow.com/questions/28409134/string-passed-into-cursor-callproc-becomes-unknown-psycopg2-python-2-7-postgr