The most recent patch (v3) applies and builds cleanly and passes make check. Documentation on the new SQL syntax and catalog changes is included with the patch and looks good to me.
The regression tests look pretty complete. In addition to the included tests, dropping and altering the data type on a column referenced in the security clause work as expected, rejecting the change with a dependency error. Renaming a column succeeds as expected.
pg_dump and restore properly was also successful.
I noticed that the security clause is visible to any user via psql \dt+, as well as in the pg_rowsecurity view. Perhaps this should be mentioned in the relevant section of user-manag.sgml so users realize any sensitive information in the security clause isn't secure.
What I've checked looks good. I don't feel qualified to do a code review so that's still outstanding. I believe Atri will be looking at that.
__________________________________________________________________________________