When the column name is an unqualified name, rather than table.column,
the error message complains about too many dotted names, which is
wrong. Report by Peter Eisentraut based on examination of the
sepgsql regression test output, but the problem also affects COMMENT.
New wording as suggested by Tom Lane.
This requires a new shared catalog, pg_shseclabel.
Along the way, fix the security_label regression tests so that they
don't monkey with the labels of any pre-existing objects. This is
unlikely to matter in practice, since only the label for the "dummy"
provider was being manipulated. But this way still seems cleaner.
KaiGai Kohei, with fairly extensive hacking by me.
This is intended as infrastructure to support integration with label-based
mandatory access control systems such as SE-Linux. Further changes (mostly
hooks) will be needed, but this is a big chunk of it.
KaiGai Kohei and Robert Haas
