+Or on Pg versions that don't support DROP CONSTRAINT and ADD PRIMARY KEY (tested on 7.1 so far):
+DROP INDEX h_part_pkg_temp_pkey;
+CREATE UNIQUE INDEX h_part_pkg_pkey ON h_part_pkg (historynum);
+select setval('h_part_pkg_temp_historynum_seq', ( select max(historynum) from h_part_pkg) );
+