-- select internal.array_unique(array['foo','bar'] || array['foo'])
create or replace function array_unique (a text[]) returns text[] as $$
  select array (
    select distinct v from unnest(a) as b(v)
  )
$$ language sql;

-- Example usage:
-- select ts, op, jsonb_pretty(mb_jsonb_diff(record, old_record))
-- from audit.record_version
-- where table_name='subscription'
-- and (record->'id')::int=1 order by ts;
create or replace function mb_jsonb_diff(record jsonb, old_record jsonb)
  returns jsonb
  language plpgsql
  as
$$
  declare
  ret jsonb;
  begin
  SELECT jsonb_object_agg(a.key, a.value)
  into ret
  FROM  ( SELECT key, value FROM jsonb_each(record)) a LEFT OUTER JOIN
        ( SELECT key, value FROM jsonb_each(old_record)) b ON a.key = b.key
    WHERE a.value != b.value OR b.key IS NULL;
  return ret;
end;
$$