Insert to correct Postgres partition dynamically using trigger, create partition automatically if not found.

gistfile1.sql

create or replace function insert_herp_to_derp()
returns trigger as $body$
declare
  name text := 'derp_' || NEW.derp_id || '_herps';
  s text;
begin
  -- check that the needed table exists on the database
  perform 1
    from pg_class, pg_namespace
    where relnamespace = pg_namespace.oid
      and relkind = 'r'::"char"
      and relname = name;

  IF NOT FOUND THEN
    BEGIN
      s := 'CREATE TABLE ' || name || ' (
          CHECK ( derp_id = ' || NEW.derp_id || ' )
        ) INHERITS ( herps )';   
      raise notice 'creating table as [%]', s;
      EXECUTE s;
    END;
  END IF;
  EXECUTE 'INSERT INTO ' || quote_ident(name) || ' SELECT ($1).*' using NEW;
  return null;
end;                                    
$body$ LANGUAGE plpgsql;

This would be better if I attempted an insert and then rescued the exception if the table doesn't exist, creating it only then. Not sure whether that's possible though.