On Thu, Feb 6, 2020 at 11:06:44AM +0100, Jürgen Purtz wrote:
>
> > There's a few things wrong about this part anyway- namely that we've got
> > FDWs now, and there's certainly other cluster-wide things that exist
> > beyond the specific items listed, so I wonder if perhaps we should just
> > stop trying to list everything here.
>
> Inspiring answer! After some inquiry I became aware, that we do not have
> only 2 levels of 'belong-to' but 3: tables, views, operators, and much more
> objects belong to a schema; schemata, extensions (e.g. FDW), and more(?)
> belong to a database; databases, roles, tablespaces, and more belong to a
> cluster. Two aspects of 'belong-to' are: object names are unique within
> their level, and objects are automatically known everywhere within their
> level.
>
> Information about such dependencies and their consequences is spread across
> different chapters of the documentation and the System Catalog. Of course
> the chapter about roles/users is not suitable to explain the details. But
> it's important to know the hierarchy, it shut be summarized somewhere.
I developed the attached patch to address this suggestion. FYI, you can
list global objects using this query:
SELECT relname
FROM pg_class JOIN pg_tablespace ON (reltablespace = pg_tablespace.oid)
WHERE relkind = 'r' and spcname = 'pg_global';
relname
-----------------------
pg_authid
pg_subscription
pg_database
pg_db_role_setting
pg_tablespace
pg_auth_members
pg_shdepend
pg_shdescription
pg_replication_origin
pg_shseclabel
--
Bruce Momjian <br...@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 8d3a0d1c22..fe5e81cd65 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -2625,19 +2625,18 @@ SELECT * FROM information WHERE group_id = 2 FOR UPDATE;
</indexterm>
<para>
- A <productname>PostgreSQL</productname> 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 <productname>PostgreSQL</productname> 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.
</para>
<note>
<para>
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, <literal>joe</literal> in two databases
+ database in the cluster. Sharing of role names means that there
+ cannot be different roles named, say, <literal>joe</literal> in two databases
in the same cluster; but the system can be configured to allow
<literal>joe</literal> access to only some of the databases.
</para>
diff --git a/doc/src/sgml/manage-ag.sgml b/doc/src/sgml/manage-ag.sgml
index b1b8539fb3..0510afd818 100644
--- a/doc/src/sgml/manage-ag.sgml
+++ b/doc/src/sgml/manage-ag.sgml
@@ -22,16 +22,13 @@
</indexterm>
<para>
- A database is a named collection of <acronym>SQL</acronym> objects
- (<quote>database objects</quote>). Generally, every database
- object (tables, functions, etc.) belongs to one and only one
- database. (However there are a few system catalogs, for example
- <literal>pg_database</literal>, 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,
- such as a function).
+ A small number of objects, like role, database, and tablespace names,
+ are stored at the cluster level and use the <literal>pg_global</literal>
+ 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).
</para>
<para>
