Question

I am trying to select arrays in a set-returning function in postgres 8.4, but receiving
the error:

“array value must start with “{” or dimension information”.

This issue appears to relate to locationnodes.rs_people_c sometimes
having an empty array. I’ve tried to get around that with a COALESCE statement. No luck.

function:

CREATE OR REPLACE FUNCTION fn_matview_location_slots (
    week_start  DATE
) RETURNS setof matview_location_slots_info AS
$$
DECLARE
    resulter    matview_location_slots_info%ROWTYPE;
BEGIN
    FOR resulter IN
        SELECT
            rs_node               AS node,
            rs_date               AS dater,
            ...
            COALESCE(rs_people_c, '{}'::INTEGER[]) AS people,
            rs_location           AS location
        FROM
            locationnodes
        WHERE
            rs_date >= week_start
    LOOP
        RETURN NEXT resulter;
    END LOOP;
END; $$ LANGUAGE plpgsql;

type:

CREATE TYPE matview_location_slots_info AS (
        node              VARCHAR,
        dater             DATE,
        ...
        people            INTEGER[],
        location          INTEGER[]
);

data

select rs_people_c from locationnodes;
           rs_people_c
-------------------------------------
 {}
 {}
 {731}
 {32}
 {31}
 {}
 {62}
 {540,72,69,53,37,42,201,51,58}
 {64}

Answer 1

I made a stupid type definition error (which I excluded from my original question, but Grzegorz alluded to — thanks Grzegorz).

I posting this as an answer for anyone who googles the problem of array value must start with “{” or dimension information.

In my case the issue was that the location return type was defined as an array of integers, but the function was returning a simple integer. Unfortunately Postgres doesn’t provide more information about the specific problem in these cases.

Also note that in this sort of case you don’t need to coalesce NULL arrays to {} as I did in my question.

In short : make sure your array return types are receiving array input!