idea: simple variadic functions in SQL and PL/pgSQL
Hello,
I found easy implementation of variadic functions. It's based on
adapation FuncnameGetCandidates. When I found variadic function, then
I should create accurate number of last arguments (diff between
pronargs and nargs). Variadic function can be signed via flag or via
some pseudotype. Flag is better - allows variadic arguments of any
type. In static languages (like SQL or PL/pgSQL) variadic variables
can ba accessed via array (variadic arguments can be only nonarray).
This isn't problem in C language, there are arguments available
directly.
Sample:
CREATE OR REPLACE FUNCTION Least(anyelement)
RETURNS anyelement AS $$
SELECT MIN($1[i])
FROM generate_series(1, array_upper($1,1)) g(i);
$$ LANGUAGE SQL IMMUTABLE VARIADIC.
This sample is really simple. The goal is support sophistic libraries
like JSON support: http://www.mysqludf.org/lib_mysqludf_json/index.php
Main change in FuncnameGetCandidates.
if (!OidIsValid(variadic_oid))
{
memcpy(newResult->args, procform->proargtypes.values,
pronargs * sizeof(Oid));
}
else
{
int j;
/* copy nonvariadic parameters */
memcpy(newResult->args, procform->proargtypes.values,
pronargs * sizeof(Oid));
/* set variadic parameters, !!!!!!!!!!! */
for (j = pronargs - 1; j < nargs; j++)
newResult->args[j] = variadic_oid;
}
I invite any ideas, notes
Regards
Pavel Stehule
Pavel Stehule wrote:
Hello,
I found easy implementation of variadic functions. It's based on
adapation FuncnameGetCandidates. When I found variadic function, then
I should create accurate number of last arguments (diff between
pronargs and nargs). Variadic function can be signed via flag or via
some pseudotype. Flag is better - allows variadic arguments of any
type. In static languages (like SQL or PL/pgSQL) variadic variables
can ba accessed via array (variadic arguments can be only nonarray).
This isn't problem in C language, there are arguments available
directly.
There are a whole slew of questions around this, ISTM.
For example: What will be the type inferred for the array of variadic
args in plpgsql?
If we are going to do this I think we need some discussion on design
before we rush into it.
cheers
andrew
Hello
On 26/02/2008, Andrew Dunstan <andrew@dunslane.net> wrote:
Pavel Stehule wrote:
Hello,
I found easy implementation of variadic functions. It's based on
adapation FuncnameGetCandidates. When I found variadic function, then
I should create accurate number of last arguments (diff between
pronargs and nargs). Variadic function can be signed via flag or via
some pseudotype. Flag is better - allows variadic arguments of any
type. In static languages (like SQL or PL/pgSQL) variadic variables
can ba accessed via array (variadic arguments can be only nonarray).
This isn't problem in C language, there are arguments available
directly.There are a whole slew of questions around this, ISTM.
sure. It's time to thing about it.
For example: What will be the type inferred for the array of variadic
args in plpgsql?
SQL and PL/SQL should be limited. In my prototype I use fragment:
/* replace ANYNONARRAYS argument with ARRAY OF some */
argtype = get_array_type(argtype);
if (!OidIsValid(argtype))
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("could not determine
actual array type for variadic argument")));
SPI is unlimited (C language). I can use list of arrays in perl or
python - there I don't see complications too. Domains and arrays can
be problem. Using variadic array variables isn't typical. So I will to
solve only domains. But it's more general problem. Maybe 8.4 can
support array of domains.
If we are going to do this I think we need some discussion on design
before we rush into it.
yes, I agree. Variadic functions are simple. And I belive it can
simplify life to some programmers that have to manage functions like:
foo(int),
foo(int, int)
foo(int, int, int)...
regards
Pavel
Show quoted text
cheers
andrew