Fix relcache for policies, and doc updates

Andres pointed out that there was an extra ';' in equalPolicies, which
made me realize that my prior testing with CLOBBER_CACHE_ALWAYS was
insufficient (it didn't always catch the issue, just most of the time).
Thanks to that, a different issue was discovered, specifically in
equalRSDescs.  This change corrects eqaulRSDescs to return 'true' once
all policies have been confirmed logically identical.  After stepping
through both functions to ensure correct behavior, I ran this for
about 12 hours of CLOBBER_CACHE_ALWAYS runs of the regression tests
with no failures.

In addition, correct a few typos in the documentation which were pointed
out by Thom Brown (thanks!) and improve the policy documentation further
by adding a flushed out usage example based on a unix passwd file.

Lastly, clean up a few comments in the regression tests and pg_dump.h.

doc/src/sgml/ddl.sgml

@@ -1615,7 +1615,7 @@ REVOKE ALL ON accounts FROM PUBLIC;
    and foreign key references, will bypass row security to ensure that
    data integrity is maintained.  Care must be taken when developing
    schemas and row level policies to avoid a "covert channel" leak of
-   information through these referntial integrity checks.
+   information through these referential integrity checks.
   </para>
 
   <para>
@@ -1674,6 +1674,115 @@ CREATE POLICY user_policy ON users
    normal privileges system.
   </para>
 
+  <para>
+   Below is a larger example of how this feature can be used in
+   production environments, based on a unix password file.
+  </para>
+
+<programlisting>
+-- Simple passwd-file based example
+CREATE TABLE passwd (
+  username              text UNIQUE NOT NULL,
+  pwhash                text,
+  uid                   int  PRIMARY KEY,
+  gid                   int  NOT NULL,
+  real_name             text NOT NULL,
+  home_phone            text,
+  extra_info            text,
+  home_dir              text NOT NULL,
+  shell                 text NOT NULL
+);
+
+CREATE ROLE admin;  -- Administrator
+CREATE ROLE bob;    -- Normal user
+CREATE ROLE alice;  -- Normal user
+
+-- Populate the table
+INSERT INTO passwd VALUES
+  ('admin','xxx',0,0,'Admin','111-222-3333',null,'/root','/bin/dash');
+INSERT INTO passwd VALUES
+  ('bob','xxx',1,1,'Bob','123-456-7890',null,'/home/bob','/bin/zsh');
+INSERT INTO passwd VALUES
+  ('alice','xxx',2,1,'Alice','098-765-4321',null,'/home/alice','/bin/zsh');
+
+-- Be sure to enable row level security on the table
+ALTER TABLE passwd ENABLE ROW LEVEL SECURITY;
+
+-- Create policies
+-- Administrator can see all rows and add any rows
+CREATE POLICY admin_all ON passwd TO admin USING (true) WITH CHECK (true);
+-- Normal users can view all rows
+CREATE POLICY all_view ON passwd FOR SELECT USING (true);
+-- Normal users can update their own records, but
+-- limit which shells a normal user is allowed to set
+CREATE POLICY user_mod ON passwd FOR UPDATE
+  USING (current_user = username)
+  WITH CHECK (
+    current_user = username AND
+    shell IN ('/bin/bash','/bin/sh','/bin/dash','/bin/zsh','/bin/tcsh')
+  );
+
+-- Allow admin all normal rights
+GRANT SELECT, INSERT, UPDATE, DELETE ON passwd TO admin;
+-- Users only get select access on public columns
+GRANT SELECT
+  (username, uid, gid, real_name, home_phone, extra_info, home_dir, shell)
+  ON passwd TO public;
+-- Allow users to update certain columns
+GRANT UPDATE
+  (pwhash, real_name, home_phone, extra_info, shell)
+  ON passwd TO public;
+</programlisting>
+
+  <para>
+   As with any security settings, it's important to test and ensure that
+   the system is behaving as expected.  Using the example above, this
+   demonstrates that the permission system is working properly.
+  </para>
+
+<programlisting>
+-- admin can view all rows and fields
+postgres=> set role admin;
+SET
+postgres=> table passwd;
+ username | pwhash | uid | gid | real_name |  home_phone  | extra_info | home_dir    |   shell   
+----------+--------+-----+-----+-----------+--------------+------------+-------------+-----------
+ admin    | xxx    |   0 |   0 | Admin     | 111-222-3333 |            | /root       | /bin/dash
+ bob      | xxx    |   1 |   1 | Bob       | 123-456-7890 |            | /home/bob   | /bin/zsh
+ alice    | xxx    |   2 |   1 | Alice     | 098-765-4321 |            | /home/alice | /bin/zsh
+(3 rows)
+
+-- Test what Alice is able to do
+postgres=> set role alice;
+SET
+postgres=> table passwd;
+ERROR:  permission denied for relation passwd
+postgres=> select username,real_name,home_phone,extra_info,home_dir,shell from passwd;
+ username | real_name |  home_phone  | extra_info | home_dir    |   shell   
+----------+-----------+--------------+------------+-------------+-----------
+ admin    | Admin     | 111-222-3333 |            | /root       | /bin/dash
+ bob      | Bob       | 123-456-7890 |            | /home/bob   | /bin/zsh
+ alice    | Alice     | 098-765-4321 |            | /home/alice | /bin/zsh
+(3 rows)
+
+postgres=> update passwd set username = 'joe';
+ERROR:  permission denied for relation passwd
+-- Allowed to change her own real_name, but no others
+postgres=> update passwd set real_name = 'Alice Doe';
+UPDATE 1
+postgres=> update passwd set real_name = 'John Doe' where username = 'admin';
+UPDATE 0
+postgres=> update passwd set shell = '/bin/xx';
+ERROR:  new row violates WITH CHECK OPTION for "passwd"
+postgres=> delete from passwd;
+ERROR:  permission denied for relation passwd
+postgres=> insert into passwd (username) values ('xxx');
+ERROR:  permission denied for relation passwd
+-- Alice can change her own password
+postgres=> update passwd set pwhash = 'abc';
+UPDATE 1
+</programlisting>
+
  </sect1>
 
  <sect1 id="ddl-schemas">

doc/src/sgml/ref/alter_policy.sgml

@@ -94,7 +94,7 @@ ALTER POLICY <replaceable class="parameter">name</replaceable> ON <replaceable c
       security-barrier qualification to queries which use the table
       automatically.  If multiple policies are being applied for a given
       table then they are all combined and added using OR.  The USING
-      expression applies to records which are being retrived from the table.
+      expression applies to records which are being retrieved from the table.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/create_policy.sgml

@@ -81,7 +81,7 @@ CREATE POLICY <replaceable class="parameter">name</replaceable> ON <replaceable
    referenced table.  These issues can be addressed by carefully crafting
    policies which prevent users from being able to insert, delete, or update
    records at all which might possibly indicate a value they are not otherwise
-   able to see, or by using generated values (eg: surrogate keys) instead.
+   able to see, or by using generated values (e.g.: surrogate keys) instead.
   </para>
 
   <para>
@@ -218,7 +218,7 @@ CREATE POLICY <replaceable class="parameter">name</replaceable> ON <replaceable
          records from the relation which pass the <literal>SELECT</literal>
          policy will be returned, even if other records exist in the relation.
          The <literal>SELECT</literal> policy only accepts the USING expression
-         as it only ever applies in cases where records are being retrived from
+         as it only ever applies in cases where records are being retrieved from
          the relation.
        </para>
       </listitem>
@@ -272,7 +272,7 @@ CREATE POLICY <replaceable class="parameter">name</replaceable> ON <replaceable
          for the <literal>DELETE</literal>, and rows which are not visible
          through the <literal>SELECT</literal> policy may be deleted if they
          pass the <literal>DELETE</literal> USING policy.  The
-         <literal>DELETE</literal> policy only accept the USING expression as
+         <literal>DELETE</literal> policy only accepts the USING expression as
          it only ever applies in cases where records are being extracted from
          the relation for deletion.
        </para>

src/backend/utils/cache/relcache.c

@@ -868,7 +868,7 @@ equalPolicy(RowSecurityPolicy *policy1, RowSecurityPolicy *policy2)
 			return false;
 		if (policy1->cmd != policy2->cmd)
 			return false;
-		if (policy1->hassublinks != policy2->hassublinks);
+		if (policy1->hassublinks != policy2->hassublinks)
 			return false;
 		if (strcmp(policy1->policy_name,policy2->policy_name) != 0)
 			return false;
@@ -926,7 +926,7 @@ equalRSDesc(RowSecurityDesc *rsdesc1, RowSecurityDesc *rsdesc2)
 			return false;
 	}
 
-	return false;
+	return true;
 }
 
 /*

src/bin/pg_dump/pg_dump.h

@@ -246,7 +246,7 @@ typedef struct _tableInfo
 	bool		hasindex;		/* does it have any indexes? */
 	bool		hasrules;		/* does it have any rules? */
 	bool		hastriggers;	/* does it have any triggers? */
-	bool		rowsec;			/* does it have any row-security policy? */
+	bool		rowsec;			/* is row-security enabled? */
 	bool		hasoids;		/* does it have OIDs? */
 	uint32		frozenxid;		/* for restore frozen xid */
 	uint32		minmxid;		/* for restore min multi xid */

src/test/regress/expected/rowsecurity.out

@@ -69,7 +69,7 @@ INSERT INTO document VALUES
     ( 7, 33, 2, 'rls_regress_user2', 'great technology book'),
     ( 8, 44, 1, 'rls_regress_user2', 'great manga');
 ALTER TABLE document ENABLE ROW LEVEL SECURITY;
--- user's security level must be higher that or equal to document's
+-- user's security level must be higher than or equal to document's
 CREATE POLICY p1 ON document
     USING (dlevel <= (SELECT seclv FROM uaccount WHERE pguser = current_user));
 -- viewpoint from rls_regress_user1
@@ -280,7 +280,7 @@ SELECT * FROM document d FULL OUTER JOIN category c on d.cid = c.cid;
 DELETE FROM category WHERE cid = 33;    -- fails with FK violation
 ERROR:  update or delete on table "category" violates foreign key constraint "document_cid_fkey" on table "document"
 DETAIL:  Key (cid)=(33) is still referenced from table "document".
--- cannot insert FK referencing invisible PK
+-- can insert FK referencing invisible PK
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document d FULL OUTER JOIN category c on d.cid = c.cid;
  did | cid | dlevel |      dauthor      |        dtitle         | cid |      cname      
@@ -301,7 +301,7 @@ SELECT * FROM document WHERE did = 8; -- and confirm we can't see it
 -----+-----+--------+---------+--------
 (0 rows)
 
--- database superuser cannot bypass RLS policy when enabled
+-- database superuser does bypass RLS policy when enabled
 RESET SESSION AUTHORIZATION;
 SET row_security TO ON;
 SELECT * FROM document;
@@ -327,7 +327,7 @@ SELECT * FROM category;
   44 | manga
 (4 rows)
 
--- database superuser cannot bypass RLS policy when FORCE enabled.
+-- database superuser does not bypass RLS policy when FORCE enabled.
 RESET SESSION AUTHORIZATION;
 SET row_security TO FORCE;
 SELECT * FROM document;
@@ -340,7 +340,7 @@ SELECT * FROM category;
 -----+-------
 (0 rows)
 
--- database superuser can bypass RLS policy when disabled
+-- database superuser does bypass RLS policy when disabled
 RESET SESSION AUTHORIZATION;
 SET row_security TO OFF;
 SELECT * FROM document;

src/test/regress/sql/rowsecurity.sql

@@ -84,7 +84,7 @@ INSERT INTO document VALUES
 
 ALTER TABLE document ENABLE ROW LEVEL SECURITY;
 
--- user's security level must be higher that or equal to document's
+-- user's security level must be higher than or equal to document's
 CREATE POLICY p1 ON document
     USING (dlevel <= (SELECT seclv FROM uaccount WHERE pguser = current_user));
 
@@ -136,7 +136,7 @@ SET SESSION AUTHORIZATION rls_regress_user1;
 SELECT * FROM document d FULL OUTER JOIN category c on d.cid = c.cid;
 DELETE FROM category WHERE cid = 33;    -- fails with FK violation
 
--- cannot insert FK referencing invisible PK
+-- can insert FK referencing invisible PK
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document d FULL OUTER JOIN category c on d.cid = c.cid;
 INSERT INTO document VALUES (10, 33, 1, current_user, 'hoge');
@@ -146,19 +146,19 @@ SET SESSION AUTHORIZATION rls_regress_user1;
 INSERT INTO document VALUES (8, 44, 1, 'rls_regress_user1', 'my third manga'); -- Must fail with unique violation, revealing presence of did we can't see
 SELECT * FROM document WHERE did = 8; -- and confirm we can't see it
 
--- database superuser cannot bypass RLS policy when enabled
+-- database superuser does bypass RLS policy when enabled
 RESET SESSION AUTHORIZATION;
 SET row_security TO ON;
 SELECT * FROM document;
 SELECT * FROM category;
 
--- database superuser cannot bypass RLS policy when FORCE enabled.
+-- database superuser does not bypass RLS policy when FORCE enabled.
 RESET SESSION AUTHORIZATION;
 SET row_security TO FORCE;
 SELECT * FROM document;
 SELECT * FROM category;
 
--- database superuser can bypass RLS policy when disabled
+-- database superuser does bypass RLS policy when disabled
 RESET SESSION AUTHORIZATION;
 SET row_security TO OFF;
 SELECT * FROM document;