Thread: Bug? Unexpected argument handling in pl-python variadic argument function
Unexpected argument handling in pl/python variadic argument function
create or replace function variadic_sql(template text, variadic args text[], out text)language sql as$$ select $1 ||
' -- ' || $2::text$$;
create or replace function variadic_python(template text, variadic args text[], out text)language plpythonu as$$
returntemplate + ' -- ' + str(args)$$;
-- expected
select variadic_sql('<html>{foo}{bar}</html>', '1', '2'); variadic_sql
------------------------------------<html>{foo}{bar}</html> -- {1,2}
-- first scalar arg also in the variadic args
select variadic_python('<html>{foo}{bar}</html>', '1', '2');
variadic_python
----------------------------------------------------------------------<html>{foo}{bar}</html> --
['<html>{foo}{bar}</html>',['1', '2']]
select version();PostgreSQL 9.0.1 on i686-pc-linux-gnu, compiled by GCC
i686-pc-linux-gnu-gcc (Gentoo 4.4.2 p1.0) 4.4.2, 32-bit
(1 row)
I could not find very much documentation and only this on the lists:
from Jan Urbański on his planned improvements for pl/python:
http://archives.postgresql.org/pgsql-hackers/2010-12/msg00551.php
> * variadic argument handling (is this possible for a non-plpgsql pl?)
Does this mean this is already a recognized flaw or it was unknown at
the time if the feature was implemented? I would definitely would not
expect the argument to duplicated. I know there is big patch for
pl/python being reviewed right now. Perhaps this is being fixed? It
would be wonderful for plpython to support complex arguments
gracefully.
--
Thanks,
Nate Carson
Re: Bug? Unexpected argument handling in pl-python variadic argument function
From
Jan Urbański
Date:
On 24/01/11 02:01, Nate C wrote:
> Unexpected argument handling in pl/python variadic argument function
>
> create or replace function variadic_sql
> (template text, variadic args text[], out text)
> language sql as
> $$
> select $1 || ' -- ' || $2::text
> $$;
>
> create or replace function variadic_python
> (template text, variadic args text[], out text)
> language plpythonu as
> $$
> return template + ' -- ' + str(args)
> $$;
>
>
> -- expected
> select variadic_sql('<html>{foo}{bar}</html>', '1', '2');
> variadic_sql
> ------------------------------------
> <html>{foo}{bar}</html> -- {1,2}
>
>
> -- first scalar arg also in the variadic args
> select variadic_python('<html>{foo}{bar}</html>', '1', '2');
>
>
> variadic_python
> ----------------------------------------------------------------------
> <html>{foo}{bar}</html> -- ['<html>{foo}{bar}</html>', ['1', '2']]
You've chosen an unfortunate name for the variadic argument: see
http://www.postgresql.org/docs/current/static/plpython-funcs.html
PL/Python functions automatically have a global "args" variable that is
a list of all the arguments. That's necessary because you can have
functions that don't assign names to variables, like
create function noname_concat(text, text) returns text language
plpythonu as $$ return args[0] + args[1]
$$;
Perhaps we should throw an error if you try to define a function with an
explicit "args" variable? It'd be a backwards-compatibility problem, but
then again these functions are probably already broken for people.
> I could not find very much documentation and only this on the lists:
>
> from Jan Urbański on his planned improvements for pl/python:
> http://archives.postgresql.org/pgsql-hackers/2010-12/msg00551.php
>
>> * variadic argument handling (is this possible for a non-plpgsql pl?)
Yes, I thought it would require some work but it turned out that the
generic mechanism already worked for variadic arguments, so there's no
need for specific PL/Python code to support them.
Cheers,
Jan