Passing an array to stored to postgres

Question

Like advised I am linking to my previous question:
PL/pgSQL control structures for lists / arrays

I want to pass a list of numbers and a list of characters into a Postgres stored procedure. After that I want to do something with those two arrays. For number list you already helped me. I used CREATE OR REPLACE FUNCTION my_proc(p_amount_list numeric[]) as input parameter, and when I called that procedure I used SELECT my_proc('{2,2,2}');.

Now I want to know how to pass a list of characters and also how to call the procedure after that.

Answer 1

You could build a function that either concatenates strings or sums up numeric values depending on the polymorphic input type:

CREATE OR REPLACE FUNCTION poly_sum_agg(_arr anyarray)
  RETURNS text AS
$func$
BEGIN

CASE (SELECT e.typcategory FROM pg_type e
      WHERE  e.oid = (SELECT typelem FROM pg_type WHERE oid = pg_typeof(_arr)))

WHEN 'S' THEN  -- string types: char, name, text, bpchar, varchar
   RETURN array_to_string(_arr, '');  -- no separator?

WHEN 'N' THEN  -- numeric: int8, int2, int4, oid, float4, float8, money, numeric
   RETURN (SELECT sum(elem)::text FROM unnest(_arr) elem);

ELSE
   RAISE EXCEPTION 'Unexpected array type!';

END CASE;

END
$func$ LANGUAGE plpgsql;

Call (note the explicit type cast):

SELECT poly_sum_agg('{1,2,3}'::int[]) AS int_arr; -- Returns '6'

Or:

SELECT poly_sum_agg('{1,2,3}'::text[]) AS text_arr; -- Returns '123'

SQL Fiddle.

This is just a proof of concept. It builds on the internal representation of array types in the system catalog pg_type and may not be portable across major releases. Here is how I retrieved information fro the system catalog:

SQL Fiddle.

It's largely unclear what your exact objective is. Depending on what you actually need, I would most probably take a different approach.