Table range partitioning

Returning to the dellstore2 example database used in Chapter 10, Query Optimization, consider the structure of the orders table:

dellstore2=# \d orders;
Table "public.orders"
   Column    |     Type      | Modifiers                         
-------------+---------------+--------------------------------
   orderid     | integer       | not null default nextval('orders_orderid_seq'::regclass)
   orderdate   | date          | not null
   customerid  | integer       | 
   netamount   | numeric(12,2) | not null
   tax         | numeric(12,2) | not null
   totalamount | numeric(12,2) | not null
Indexes:
   "orders_pkey" PRIMARY KEY, btree (orderid)
   "ix_order_custid" btree (customerid)
Foreign-key constraints:
   "fk_customerid" FOREIGN KEY (customerid) REFERENCES customers(customerid) ON DELETE SET NULL
Referenced by:
   TABLE "orderlines" CONSTRAINT "fk_orderid" FOREIGN KEY (orderid) REFERENCES orders(orderid) ON DELETE CASCADE
  

Imagine that after many years of operation...