Doc: improve documentation of pg_signal_backend default role.

Give it an explanatory para like the other default roles have.
Don't imply that it can send any signal whatever.

In passing, reorder the table entries and explanatory paras
for the default roles into some semblance of consistency.

Ian Barwick, tweaked a bit by me.

Discussion: https://postgr.es/m/89907e32-76f3-7282-a89c-ea19c722fe5d@2ndquadrant.com

diff --git a/doc/src/sgml/user-manag.sgml b/doc/src/sgml/user-manag.sgml
index 357f25df0dfdd2f7155f7ad7cadb0ec06abf4e9f..cf41baa2063cf83d4afcee28c7c7921e0c494dee 100644 (file)
--- a/doc/src/sgml/user-manag.sgml
+++ b/doc/src/sgml/user-manag.sgml
@@ -530,10 +530,6 @@ DROP ROLE doomed_role;
        Execute monitoring functions that may take ACCESS SHARE locks on tables,
        potentially for a long time.
       
-      
-       pg_signal_backend
-       Send signals to other backends (eg: cancel query, terminate).
-      
       
        pg_monitor
        Read/execute various monitoring views and functions.
@@ -541,6 +537,10 @@ DROP ROLE doomed_role;
        pg_read_all_stats and
        pg_stat_scan_tables.
       
+      
+       pg_signal_backend
+       Signal another backend to cancel a query or terminate its session.
+      
      
     
    
@@ -554,14 +554,23 @@ DROP ROLE doomed_role;
   other system information normally restricted to superusers.
   
 
+  
+  The pg_signal_backend role is intended to allow
+  administrators to enable trusted, but non-superuser, roles to send signals
+  to other backends. Currently this role enables sending of signals for
+  canceling a query on another backend or terminating its session. A user
+  granted this role cannot however send signals to a backend owned by a
+  superuser.  See .
+  
+
   
   Care should be taken when granting these roles to ensure they are only used where
   needed to perform the desired monitoring.
   
 
   
-   Administrators can grant access to these roles to users using the GRANT
-   command:
+   Administrators can grant access to these roles to users using the
+    command, for example:
 
 
 GRANT pg_signal_backend TO admin_user;