doc: clarify hierarchy of objects: global, db, schema, etc.

The previous wording was confusing because it wasn't in decreasing order
and had to backtrack.  Also clarify role/user wording.

Reported-by: [email protected]
Discussion: https://postgr.es/m/158057750885.1123.2806779262588618988@wrigleys.postgresql.org

Backpatch-through: 9.5

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index b2cad3384294832d27af0046472e36d3d8e9c5f6..7dbd1008d78ea1117b6adbe78057892964a312ea 100644 (file)
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -2618,19 +2618,18 @@ SELECT * FROM information WHERE group_id = 2 FOR UPDATE;
   
 
   
-   A PostgreSQL database cluster
-   contains one or more named databases.  Users and groups of users are
-   shared across the entire cluster, but no other data is shared across
-   databases.  Any given client connection to the server can access
-   only the data in a single database, the one specified in the connection
-   request.
+   A PostgreSQL database cluster contains
+   one or more named databases.  Roles and a few other object types are
+   shared across the entire cluster.  A client connection to the server
+   can only access data in a single database, the one specified in the
+   connection request.
   
 
   
    
     Users of a cluster do not necessarily have the privilege to access every
-    database in the cluster.  Sharing of user names means that there
-    cannot be different users named, say, joe in two databases
+    database in the cluster.  Sharing of role names means that there
+    cannot be different roles named, say, joe in two databases
     in the same cluster; but the system can be configured to allow
     joe access to only some of the databases.
    

diff --git a/doc/src/sgml/manage-ag.sgml b/doc/src/sgml/manage-ag.sgml
index 0154064e506306eda0ca848b960752ecc217a650..985e625bbccdb1b5c960e28bad0b2aa97a028ced 100644 (file)
--- a/doc/src/sgml/manage-ag.sgml
+++ b/doc/src/sgml/manage-ag.sgml
@@ -22,15 +22,13 @@
   
 
   
-   A database is a named collection of SQL objects
-   (database objects).  Generally, every database
-   object (tables, functions, etc.) belongs to one and only one
-   database.  (However there are a few system catalogs, for example
-   pg_database, that belong to a whole cluster and
-   are accessible from each database within the cluster.)  More
-   accurately, a database is a collection of schemas and the schemas
-   contain the tables, functions, etc.  So the full hierarchy is:
-   server, database, schema, table (or some other kind of object,
+   A small number of objects, like role, database, and tablespace
+   names, are defined at the cluster level and stored in the
+   pg_global tablespace.  Inside the cluster are
+   multiple databases, which are isolated from each other but can access
+   cluster-level objects.  Inside each database are multiple schemas,
+   which contain objects like tables and functions.  So the full hierarchy
+   is: cluster, database, schema, table (or some other kind of object,
    such as a function).