Change ALTER TABLE SET WITHOUT OIDS to rewrite the whole table to physically

get rid of the OID column.  This eliminates the problem discovered by Heikki
back in November that 8.4's suppression of "unnecessary" junk filtering in
INSERT/SELECT could lead to an Assert failure, or storing of oids into a table
that shouldn't have them if Asserts are off.  While that particular problem
could have been solved in other ways, it seems likely to be just a forerunner
of things to come if we continue to allow tables to contain rows that disagree
with the pg_class.relhasoids setting.  It's better to make this operation slow
than to sacrifice performance or risk bugs in more common code paths.

Also, add ALTER TABLE SET WITH OIDS to rewrite the table to add oids.
This was a bit more controversial, but in view of the very small amount of
extra code needed given the current ALTER TABLE infrastructure, it seems best
to eliminate the asymmetry in features.

src/test/regress/sql/alter_table.sql

@@ -921,7 +921,7 @@ order by relname, attnum;
 drop table p1, p2 cascade;
 
 --
--- Test the ALTER TABLE WITHOUT OIDS command
+-- Test the ALTER TABLE SET WITH/WITHOUT OIDS command
 --
 create table altstartwith (col integer) with oids;
 
@@ -934,10 +934,16 @@ alter table altstartwith set without oids;
 select oid > 0, * from altstartwith; -- fails
 select * from altstartwith;
 
--- Run inheritance tests
+alter table altstartwith set with oids;
+
+select oid > 0, * from altstartwith;
+
+drop table altstartwith;
+
+-- Check inheritance cases
 create table altwithoid (col integer) with oids;
 
--- Inherits parents oid column
+-- Inherits parents oid column anyway
 create table altinhoid () inherits (altwithoid) without oids;
 
 insert into altinhoid values (1);
@@ -946,13 +952,42 @@ select oid > 0, * from altwithoid;
 select oid > 0, * from altinhoid;
 
 alter table altwithoid set without oids;
-alter table altinhoid set without oids;
 
 select oid > 0, * from altwithoid; -- fails
 select oid > 0, * from altinhoid; -- fails
 select * from altwithoid;
 select * from altinhoid;
 
+alter table altwithoid set with oids;
+
+select oid > 0, * from altwithoid;
+select oid > 0, * from altinhoid;
+
+drop table altwithoid cascade;
+
+create table altwithoid (col integer) without oids;
+
+-- child can have local oid column
+create table altinhoid () inherits (altwithoid) with oids;
+
+insert into altinhoid values (1);
+
+select oid > 0, * from altwithoid; -- fails
+select oid > 0, * from altinhoid;
+
+alter table altwithoid set with oids;
+
+select oid > 0, * from altwithoid;
+select oid > 0, * from altinhoid;
+
+-- the child's local definition should remain
+alter table altwithoid set without oids;
+
+select oid > 0, * from altwithoid; -- fails
+select oid > 0, * from altinhoid;
+
+drop table altwithoid cascade;
+
 -- test renumbering of child-table columns in inherited operations
 
 create table p1 (f1 int);