Mark some columns in pg_subscription as NOT NULL.
Mark some columns in pg_subscription as NOT NULL.

In pg_subscription, subconninfo, subslotname, subsynccommit and
subpublications are expected not to be NULL. Therefore this patch
adds BKI_FORCE_NOT_NULL markings to them.

This patch is basically unnecessary unless the code has a bug which
wrongly sets either of those columns to NULL. But it's good to have
this as a safeguard.

Author: Masahiko Sawada
Reviewed-by: Kyotaro Horiguchi
Reported-by: Fujii Masao
Discussion: 0b9ebf7cf8a42c97a8a01ae95ccb482c4ad43e32@mail.gmail.com

xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,50wu/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,50wu/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,xinzweb/gpdb,xinzweb/gpdb,50wu/gpdb