@@ -170,8 +170,6 @@ adjusted using the configuration option <option>--with-segsize</option>
170170when building <productname>PostgreSQL</>.)
171171In principle, free space map and visibility map forks could require multiple
172172segments as well, though this is unlikely to happen in practice.
173- The contents of tables and indexes are discussed further in
174- <xref linkend="storage-page-layout">.
175173</para>
176174
177175<para>
@@ -183,15 +181,27 @@ its <acronym>TOAST</> table, if any.
183181See <xref linkend="storage-toast"> for more information.
184182</para>
185183
184+ <para>
185+ The contents of tables and indexes are discussed further in
186+ <xref linkend="storage-page-layout">.
187+ </para>
188+
186189<para>
187190Tablespaces make the scenario more complicated. Each user-defined tablespace
188191has a symbolic link inside the <varname>PGDATA</><filename>/pg_tblspc</>
189- directory, which points to the physical tablespace directory (as specified in
190- its <command>CREATE TABLESPACE</> command). The symbolic link is named after
192+ directory, which points to the physical tablespace directory (i.e., the
193+ location specified in the tablespace's <command>CREATE TABLESPACE</> command).
194+ This symbolic link is named after
191195the tablespace's OID. Inside the physical tablespace directory there is
196+ a subdirectory with a name that depends on the <productname>PostgreSQL</>
197+ server version, such as <literal>PG_9.0_201008051</>. (The reason for using
198+ this subdirectory is so that successive versions of the database can use
199+ the same <command>CREATE TABLESPACE</> location value without conflicts.)
200+ Within the version-specific subdirectory, there is
192201a subdirectory for each database that has elements in the tablespace, named
193- after the database's OID. Tables within that directory follow the filenode
194- naming scheme. The <literal>pg_default</> tablespace is not accessed through
202+ after the database's OID. Tables and indexes are stored within that
203+ directory, using the filenode naming scheme.
204+ The <literal>pg_default</> tablespace is not accessed through
195205<filename>pg_tblspc</>, but corresponds to
196206<varname>PGDATA</><filename>/base</>. Similarly, the <literal>pg_global</>
197207tablespace is not accessed through <filename>pg_tblspc</>, but corresponds to