how do I pass a user defined type variable to a function as a parameter?

Question

I want to pass a user defined type parameter to a PLPGSQL function, but I am getting this error at runtime:

dev=# select process_shapes();
ERROR:  invalid input syntax for integer: "(,,7)"
CONTEXT:  PL/pgSQL function process_shapes() line 9 at SQL statement
dev=# 

For some reason, the parameters are not passed correctly and I have no idea why it doesn't work.

My functions are:

CREATE OR REPLACE FUNCTION join_shapes(first_shape shape_t,second_shape shape_t,OUT new_shape shape_t) 
AS $$
DECLARE
BEGIN   -- simplified join_shape()s function
    new_shape.num_lines:=first_shape.num_lines+second_shape.num_lines;
END;
$$ LANGUAGE PLPGSQL;


CREATE OR REPLACE FUNCTION process_shapes() 
RETURNS void AS $$
DECLARE
    rectangle       shape_t;
    triangle        shape_t;
    produced_shape  shape_t;
BEGIN
    rectangle.num_lines:=4;
    triangle.num_lines:=3;
    SELECT join_shapes(rectangle,triangle) INTO produced_shape;
    RAISE NOTICE 'produced shape = %s',produced_shape;
END;
$$ LANGUAGE PLPGSQL;

Type definition:

CREATE TYPE shape_t AS (
    shape_id            integer,
    shape_name          varchar,
    num_lines           integer
);

Postgres version: 9.6.1

Answer 1

When the target of a SELECT ... INTO statement is of a composite type, it will assign each of the columns returned by the SELECT to a different field in the target.

However, SELECT join_shapes(rectangle,triangle) returns a single column of type shape_t , and it's trying to cram the whole thing into the first column of the target, ie produced_shape.shape_id (hence the error message about a failed integer conversion).

Instead, you need a SELECT statement which returns three columns. Just replace

SELECT join_shapes(rectangle,triangle)

with

SELECT * FROM join_shapes(rectangle,triangle)

Alternatively, you could use

produced_shape := (SELECT join_shapes(rectangle,triangle));

which performs a single assignment, rather than trying to assign the target fields individually.

Answer 2

For other people whom want to pass composite types to functions:

create type pref_public.create_test_row_input as (
  name text
);

create or replace function pref_public.create_test_row(test_row pref_public.create_test_row_input) returns pref_public.test_rows as $$
    insert into pref_public.test_rows (name)
      values
        (test_row.name)
    returning *;
  $$ language sql strict security definer;
grant execute on function pref_public.create_test_row to pref_user;

You'll need to use row()

select * from pref_public.create_test_row(row('new row'));

More info here