Improve documentation of the role-dropping process.

In general one may have to run both REASSIGN OWNED and DROP OWNED to get
rid of all the dependencies of a role to be dropped.  This was alluded to
in the REASSIGN OWNED man page, but not really spelled out in full; and in
any case the procedure ought to be documented in a more prominent place
than that.  Add a section to the "Database Roles" chapter explaining this,
and do a bit of wordsmithing in the relevant commands' man pages.

doc/src/sgml/ref/drop_owned.sgml

@@ -90,19 +90,24 @@ DROP OWNED BY { <replaceable class="PARAMETER">name</replaceable> | CURRENT_USER
   <para>
    The <xref linkend="sql-reassign-owned"> command is an alternative that
    reassigns the ownership of all the database objects owned by one or
-   more roles.
+   more roles.  However, <command>REASSIGN OWNED</> does not deal with
+   privileges for other objects.
   </para>
 
   <para>
    Databases and tablespaces owned by the role(s) will not be removed.
   </para>
+
+  <para>
+   See <xref linkend="role-removal"> for more discussion.
+  </para>
  </refsect1>
 
  <refsect1>
   <title>Compatibility</title>
 
   <para>
-   The <command>DROP OWNED</command> statement is a
+   The <command>DROP OWNED</command> command is a
    <productname>PostgreSQL</productname> extension.
   </para>
  </refsect1>

doc/src/sgml/ref/drop_role.sgml

@@ -39,10 +39,10 @@ DROP ROLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...
    A role cannot be removed if it is still referenced in any database
    of the cluster; an error will be raised if so.  Before dropping the role,
    you must drop all the objects it owns (or reassign their ownership)
-   and revoke any privileges the role has been granted. The <xref
+   and revoke any privileges the role has been granted on other objects.
-   linkend="sql-reassign-owned">
+   The <xref linkend="sql-reassign-owned"> and <xref linkend="sql-drop-owned">
-   and <xref linkend="sql-drop-owned">
+   commands can be useful for this purpose; see <xref linkend="role-removal">
-   commands can be useful for this purpose.
+   for more discussion.
   </para>
 
   <para>

doc/src/sgml/ref/drop_user.sgml

@@ -29,7 +29,7 @@ DROP USER [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...
   <title>Description</title>
 
   <para>
-   <command>DROP USER</command> is now an alias for
+   <command>DROP USER</command> is simply an alternate spelling of
    <xref linkend="sql-droprole">.
   </para>
  </refsect1>

doc/src/sgml/ref/reassign_owned.sgml

@@ -31,8 +31,9 @@ REASSIGN OWNED BY { <replaceable class="PARAMETER">old_role</replaceable> | CURR
 
   <para>
    <command>REASSIGN OWNED</command> instructs the system to change
-   the ownership of database objects owned by one of the
+   the ownership of database objects owned by any of the
-   old_roles, to new_role.
+   <replaceable class="PARAMETER">old_roles</replaceable> to
+   <replaceable class="PARAMETER">new_role</replaceable>.
   </para>
  </refsect1>
 
@@ -82,16 +83,18 @@ REASSIGN OWNED BY { <replaceable class="PARAMETER">old_role</replaceable> | CURR
 
   <para>
    The <xref linkend="sql-drop-owned"> command is an alternative that
-   drops all the database objects owned by one or more roles. Note
+   simply drops all the database objects owned by one or more roles.
-   also that <command>DROP OWNED</command> requires privileges only
-   on the source role(s).
   </para>
 
   <para>
-   The <command>REASSIGN OWNED</command> command does not affect the
+   The <command>REASSIGN OWNED</command> command does not affect any
-   privileges granted to the old_roles in objects that are not owned
+   privileges granted to the <replaceable class="PARAMETER">old_roles</> for
-   by them.  Use <command>DROP OWNED</command> to revoke those
+   objects that are not owned by them.  Use <command>DROP OWNED</command> to
-   privileges.
+   revoke such privileges.
+  </para>
+
+  <para>
+   See <xref linkend="role-removal"> for more discussion.
   </para>
 
  </refsect1>
@@ -100,7 +103,7 @@ REASSIGN OWNED BY { <replaceable class="PARAMETER">old_role</replaceable> | CURR
   <title>Compatibility</title>
 
   <para>
-   The <command>REASSIGN OWNED</command> statement is a
+   The <command>REASSIGN OWNED</command> command is a
    <productname>PostgreSQL</productname> extension.
   </para>
  </refsect1>

doc/src/sgml/user-manag.sgml

@@ -7,8 +7,8 @@
   <productname>PostgreSQL</productname> manages database access permissions
   using the concept of <firstterm>roles</>.  A role can be thought of as
   either a database user, or a group of database users, depending on how
-  the role is set up.  Roles can own database objects (for example,
+  the role is set up.  Roles can own database objects (for example, tables
-  tables) and can assign privileges on those objects to other roles to
+  and functions) and can assign privileges on those objects to other roles to
   control who has access to which objects.  Furthermore, it is possible
   to grant <firstterm>membership</> in a role to another role, thus
   allowing the member role to use privileges assigned to another role.
@@ -213,7 +213,7 @@ CREATE USER <replaceable>name</replaceable>;
        <para>
         A role must explicitly be given permission to initiate streaming
         replication (except for superusers, since those bypass all permission
-        checks). A role used for streaming replication must always
+        checks). A role used for streaming replication must
         have <literal>LOGIN</> permission as well. To create such a role, use
         <literal>CREATE ROLE <replaceable>name</replaceable> REPLICATION
         LOGIN</literal>.
@@ -408,9 +408,67 @@ RESET ROLE;
 DROP ROLE <replaceable>name</replaceable>;
 </synopsis>
    Any memberships in the group role are automatically revoked (but the
-   member roles are not otherwise affected).  Note however that any objects
+   member roles are not otherwise affected).
-   owned by the group role must first be dropped or reassigned to other
+  </para>
-   owners; and any permissions granted to the group role must be revoked.
+ </sect1>
+
+ <sect1 id="role-removal">
+  <title>Dropping Roles</title>
+
+  <para>
+   Because roles can own database objects and can hold privileges
+   to access other objects, dropping a role is often not just a matter of a
+   quick <xref linkend="sql-droprole">.  Any objects owned by the role must
+   first be dropped or reassigned to other owners; and any permissions
+   granted to the role must be revoked.
+  </para>
+
+  <para>
+   Ownership of objects can be transferred one at a time
+   using <command>ALTER</> commands, for example:
+<programlisting>
+ALTER TABLE bobs_table OWNER TO alice;
+</programlisting>
+   Alternatively, the <xref linkend="sql-reassign-owned"> command can be
+   used to reassign ownership of all objects owned by the role-to-be-dropped
+   to a single other role.  Because <command>REASSIGN OWNED</> can only
+   access objects in the current database, it is necessary to run it in each
+   database that contains objects owned by the role.
+  </para>
+
+  <para>
+   Once any valuable objects have been transferred to new owners, any
+   remaining objects owned by the role-to-be-dropped can be dropped with
+   the <xref linkend="sql-drop-owned"> command.  Again, this command can
+   only access objects in the current database, so it is necessary to run it
+   in each database that contains objects owned by the role.
+  </para>
+
+  <para>
+   <command>DROP OWNED</> also takes care of removing any privileges granted
+   to the target role for objects that do not belong to it.
+   Because <command>REASSIGN OWNED</> does not touch such objects, it's
+   typically necessary to run both <command>REASSIGN OWNED</>
+   and <command>DROP OWNED</> (in that order!) to fully remove the
+   dependencies of a role to be dropped.
+  </para>
+
+  <para>
+   In short then, the most general recipe for removing a role that has been
+   used to own objects is:
+
+  </para>
+<programlisting>
+REASSIGN OWNED BY doomed_role TO successor_role;
+DROP OWNED BY doomed_role;
+-- repeat the above commands in each database of the cluster
+DROP ROLE doomed_role;
+</programlisting>
+
+  <para>
+   If <command>DROP ROLE</> is attempted while dependent objects still
+   remain, it will issue messages identifying which objects need to be
+   reassigned or dropped.
   </para>
  </sect1>