@@ -174,8 +174,6 @@ adjusted using the configuration option <option>--with-segsize</option>
174174when building <productname>PostgreSQL</>.)
175175In principle, free space map and visibility map forks could require multiple
176176segments as well, though this is unlikely to happen in practice.
177- The contents of tables and indexes are discussed further in
178- <xref linkend="storage-page-layout">.
179177</para>
180178
181179<para>
@@ -187,15 +185,27 @@ its <acronym>TOAST</> table, if any.
187185See <xref linkend="storage-toast"> for more information.
188186</para>
189187
188+ <para>
189+ The contents of tables and indexes are discussed further in
190+ <xref linkend="storage-page-layout">.
191+ </para>
192+
190193<para>
191194Tablespaces make the scenario more complicated. Each user-defined tablespace
192195has a symbolic link inside the <varname>PGDATA</><filename>/pg_tblspc</>
193- directory, which points to the physical tablespace directory (as specified in
194- its <command>CREATE TABLESPACE</> command). The symbolic link is named after
196+ directory, which points to the physical tablespace directory (i.e., the
197+ location specified in the tablespace's <command>CREATE TABLESPACE</> command).
198+ This symbolic link is named after
195199the tablespace's OID. Inside the physical tablespace directory there is
200+ a subdirectory with a name that depends on the <productname>PostgreSQL</>
201+ server version, such as <literal>PG_9.0_201008051</>. (The reason for using
202+ this subdirectory is so that successive versions of the database can use
203+ the same <command>CREATE TABLESPACE</> location value without conflicts.)
204+ Within the version-specific subdirectory, there is
196205a subdirectory for each database that has elements in the tablespace, named
197- after the database's OID. Tables within that directory follow the filenode
198- naming scheme. The <literal>pg_default</> tablespace is not accessed through
206+ after the database's OID. Tables and indexes are stored within that
207+ directory, using the filenode naming scheme.
208+ The <literal>pg_default</> tablespace is not accessed through
199209<filename>pg_tblspc</>, but corresponds to
200210<varname>PGDATA</><filename>/base</>. Similarly, the <literal>pg_global</>
201211tablespace is not accessed through <filename>pg_tblspc</>, but corresponds to