CREATE TABLE LIKE INCLUDING POLICIES

hi.

demo:

CREATE TABLE coll_t (c) AS VALUES ('bar'::text);
CREATE POLICY coll_p ON coll_t USING (c < ('foo'::text COLLATE "C"));
+-- coll_t1 row security is not enabled, but we still copy it's policies
+CREATE TABLE coll_t1(LIKE coll_t INCLUDING POLICIES);
+\d coll_t1
+ Table "regress_rls_schema.coll_t1"
+ Column | Type | Collation | Nullable | Default
+--------+------+-----------+----------+---------
+ c | text | | |
+Policies (row security disabled):
+ POLICY "coll_p"
+ USING ((c < ('foo'::text COLLATE "C")))

by default, new table row security will be disabled, policy object comments are
copied if INCLUDING COMMENTS is specified.

ALTER TABLE SET DATA TYPE, changing a column type typically pulls the object and
reconstructs the corresponding CREATE or ALTER command string.
however CREATE TABLE LIKE retrieves the object’s catalog data and adjusts Vars
to build a Create.*Stmt node.

Here, we generate a CreatePolicyStmt from the source relation’s pg_policy
metadata and then pass it to CreatePolicy.

CreatePolicy normally performs parse analysis on CreatePolicyStmt->qual and
CreatePolicyStmt->with_check. However, since the pg_policy entries from the
source relation already have their qual and check_qual parse analyzed, we cannot
re-analyze them. Similar to transformStatsStmt, we therefore need a
transformPolicyStmt.

v1-0001: refactor CreatePolicy, add function transformPolicyStmt
briefly explained in [1].
v1-0002: CREATE TABLE LIKE INCLUDING-POLICIES

[1] https://postgr.es/m/CACJufxGPcBzdL9T6Qh=OFecN8zqxuU0QXfYF8F3WYV=uzwYCdA@mail.gmail.com