PostgreSQL array helper functions

array_helpers.sql

CREATE OR REPLACE FUNCTION array_distinct(anyarray) RETURNS anyarray AS $$
    SELECT coalesce(array_agg(x.value ORDER BY x.pos), '{}')
    FROM (
        SELECT DISTINCT ON (item.value) item.value, item.pos
        FROM unnest($1) WITH ORDINALITY item(value, pos)
    ) x
$$ LANGUAGE SQL

CREATE OR REPLACE FUNCTION array_set(anyarray) RETURNS anyarray AS $$
    SELECT coalesce(array_agg(x.v), '{}')
    FROM (SELECT DISTINCT unnest($1) AS v ORDER BY 1) x
$$ LANGUAGE SQL