Log Message:
-----------
Fix ALTER TABLE to check pre-existing NOT NULL constraints when rewriting
a table. Otherwise a USING clause that yields NULL can leave the table
violating its constraint (possibly there are other cases too). Per report
from Alexander Pravking.
Modified Files:
--------------
pgsql/src/backend/commands:
tablecmds.c (r1.192 -> r1.193)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.192&r2=1.193)