RLS makes COPY TO process child tables

While working on [1] I noticed that if RLS gets enabled, the COPY TO command
includes the contents of child table into the result, although the
documentation says it should not:

"COPY TO can be used only with plain tables, not views, and does not
copy rows from child tables or child partitions. For example, COPY
table TO copies the same rows as SELECT * FROM ONLY table. The syntax
COPY (SELECT * FROM table) TO ... can be used to dump all of the rows
in an inheritance hierarchy, partitioned table, or view."

A test case is attached (rls.sql) as well as fix proposal
(copy_rls_no_inh.diff).

[1] https://commitfest.postgresql.org/41/3641/

--
Antonin Houska
Web: https://www.cybertec-postgresql.com