-<!-- $PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.54 2007/06/03 17:05:52 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.55 2007/11/04 19:43:33 momjian Exp $ -->
<chapter id="managing-databases">
<title>Managing Databases</title>
<primary>tablespace</primary>
</indexterm>
-
Tablespaces in <productname>PostgreSQL</> allow database administrators to
- define locations in the file system where the files representing
- database objects can be stored. Once created, a tablespace can be referred
- to by name when creating database objects.
- </para>
+ <para>
+ Tablespaces in <productname>PostgreSQL</> allow database administrators to
+ define locations in the file system where the files representing
+ database objects can be stored. Once created, a tablespace can be referred
+ to by name when creating database objects.
+ </para>
- By using tablespaces, an administrator can control the disk layout
-
of a <productname>PostgreSQL</> installation. This is useful in at
- least two ways. First, if the partition or volume on which the
- cluster was initialized runs out of space and cannot be extended,
- a tablespace can be created on a different partition and used
- until the system can be reconfigured.
- </para>
+ <para>
+ By using tablespaces, an administrator can control the disk layout
+ of a <productname>PostgreSQL</> installation. This is useful in at
+ least two ways. First, if the partition or volume on which the
+ cluster was initialized runs out of space and cannot be extended,
+ a tablespace can be created on a different partition and used
+ until the system can be reconfigured.
+ </para>
- Second, tablespaces allow an administrator to use knowledge of the
- usage pattern of database objects to optimize performance. For
- example, an index which is very heavily used can be placed on a
- very fast, highly available disk, such as an expensive solid state
- device. At the same time a table storing archived data which is
- rarely used or not performance critical could be stored on a less
- expensive, slower disk system.
- </para>
+ <para>
+ Second, tablespaces allow an administrator to use knowledge of the
+ usage pattern of database objects to optimize performance. For
+ example, an index which is very heavily used can be placed on a
+ very fast, highly available disk, such as an expensive solid state
+ device. At the same time a table storing archived data which is
+ rarely used or not performance critical could be stored on a less
+ expensive, slower disk system.
+ </para>
- To define a tablespace, use the <xref
- linkend="sql-createtablespace" endterm="sql-createtablespace-title">
-
command, for example:<indexterm><primary>CREATE TABLESPACE</></>:
+ <para>
+ To define a tablespace, use the <xref
+ linkend="sql-createtablespace" endterm="sql-createtablespace-title">
+ command, for example:<indexterm><primary>CREATE TABLESPACE</></>:
<programlisting>
CREATE TABLESPACE fastspace LOCATION '/mnt/sda1/postgresql/data';
</programlisting>
- The location must be an existing, empty directory that is owned by
- the <productname>PostgreSQL</> system user. All objects subsequently
- created within the tablespace will be stored in files underneath this
- directory.
- </para>
-
- <note>
- <para>
- There is usually not much point in making more than one
- tablespace per logical file system, since you cannot control the location
- of individual files within a logical file system. However,
- <productname>PostgreSQL</> does not enforce any such limitation, and
- indeed it is not directly aware of the file system boundaries on your
- system. It just stores files in the directories you tell it to use.
- </para>
- </note>
+ The location must be an existing, empty directory that is owned by
+ the <productname>PostgreSQL</> system user. All objects subsequently
+ created within the tablespace will be stored in files underneath this
+ directory.
+ </para>
+ <note>
<para>
- Creation of the tablespace itself must be done as a database superuser,
- but after that you can allow ordinary database users to make use of it.
- To do that, grant them the <literal>CREATE</> privilege on it.
+ There is usually not much point in making more than one
+ tablespace per logical file system, since you cannot control the location
+ of individual files within a logical file system. However,
+ <productname>PostgreSQL</> does not enforce any such limitation, and
+ indeed it is not directly aware of the file system boundaries on your
+ system. It just stores files in the directories you tell it to use.
</para>
+ </note>
- <para>
- Tables, indexes, and entire databases can be assigned to
- particular tablespaces. To do so, a user with the <literal>CREATE</>
- privilege on a given tablespace must pass the tablespace name as a
- parameter to the relevant command. For example, the following creates
- a table in the tablespace <literal>space1</>:
+ <para>
+ Creation of the tablespace itself must be done as a database superuser,
+ but after that you can allow ordinary database users to make use of it.
+ To do that, grant them the <literal>CREATE</> privilege on it.
+ </para>
+
+ <para>
+ Tables, indexes, and entire databases can be assigned to
+ particular tablespaces. To do so, a user with the <literal>CREATE</>
+ privilege on a given tablespace must pass the tablespace name as a
+ parameter to the relevant command. For example, the following creates
+ a table in the tablespace <literal>space1</>:
<programlisting>
CREATE TABLE foo(i int) TABLESPACE space1;
</programlisting>
- </para>
+ </para>
- Alternatively, use the <xref linkend="guc-default-tablespace"> parameter:
+ <para>
+ Alternatively, use the <xref linkend="guc-default-tablespace"> parameter:
<programlisting>
SET default_tablespace = space1;
CREATE TABLE foo(i int);
</programlisting>
- When <varname>default_tablespace</> is set to anything but an empty
- string, it supplies an implicit <literal>TABLESPACE</> clause for
- <command>CREATE TABLE</> and <command>CREATE INDEX</> commands that
- do not have an explicit one.
- </para>
+ When <varname>default_tablespace</> is set to anything but an empty
+ string, it supplies an implicit <literal>TABLESPACE</> clause for
+ <command>CREATE TABLE</> and <command>CREATE INDEX</> commands that
+ do not have an explicit one.
+ </para>
- There is also a <xref linkend="guc-temp-tablespaces"> parameter, which
- determines the placement of temporary tables and indexes, as well as
- temporary files that are used for purposes such as sorting large data
- sets. This can be a list of tablespace names, rather than only one,
- so that the load associated with temporary objects can be spread over
- multiple tablespaces. A random member of the list is picked each time
- a temporary object is to be created.
- </para>
+ <para>
+ There is also a <xref linkend="guc-temp-tablespaces"> parameter, which
+ determines the placement of temporary tables and indexes, as well as
+ temporary files that are used for purposes such as sorting large data
+ sets. This can be a list of tablespace names, rather than only one,
+ so that the load associated with temporary objects can be spread over
+ multiple tablespaces. A random member of the list is picked each time
+ a temporary object is to be created.
+ </para>
- The tablespace associated with a database is used to store the system
- catalogs of that database. Furthermore, it is the default tablespace
- used for tables, indexes, and temporary files created within the database,
- if no <literal>TABLESPACE</> clause is given and no other selection is
- specified by <varname>default_tablespace</> or
- <varname>temp_tablespaces</> (as appropriate).
- If a database is created without specifying a tablespace for it,
- it uses the same tablespace as the template database it is copied from.
- </para>
+ <para>
+ The tablespace associated with a database is used to store the system
+ catalogs of that database. Furthermore, it is the default tablespace
+ used for tables, indexes, and temporary files created within the database,
+ if no <literal>TABLESPACE</> clause is given and no other selection is
+ specified by <varname>default_tablespace</> or
+ <varname>temp_tablespaces</> (as appropriate).
+ If a database is created without specifying a tablespace for it,
+ it uses the same tablespace as the template database it is copied from.
+ </para>
- Two tablespaces are automatically created by <literal>initdb</>. The
- <literal>pg_global</> tablespace is used for shared system catalogs. The
- <literal>pg_default</> tablespace is the default tablespace of the
- <literal>template1</> and <literal>template0</> databases (and, therefore,
- will be the default tablespace for other databases as well, unless
- overridden by a <literal>TABLESPACE</> clause in <command>CREATE
- DATABASE</>).
- </para>
+ <para>
+ Two tablespaces are automatically created by <literal>initdb</>. The
+ <literal>pg_global</> tablespace is used for shared system catalogs. The
+ <literal>pg_default</> tablespace is the default tablespace of the
+ <literal>template1</> and <literal>template0</> databases (and, therefore,
+ will be the default tablespace for other databases as well, unless
+ overridden by a <literal>TABLESPACE</> clause in <command>CREATE
+ DATABASE</>).
+ </para>
- Once created, a tablespace can be used from any database, provided
- the requesting user has sufficient privilege. This means that a tablespace
- cannot be dropped until all objects in all databases using the tablespace
- have been removed.
- </para>
+ <para>
+ Once created, a tablespace can be used from any database, provided
+ the requesting user has sufficient privilege. This means that a tablespace
+ cannot be dropped until all objects in all databases using the tablespace
+ have been removed.
+ </para>
- To remove an empty tablespace, use the <xref
- linkend="sql-droptablespace" endterm="sql-droptablespace-title">
- command.
- </para>
+ <para>
+ To remove an empty tablespace, use the <xref
+ linkend="sql-droptablespace" endterm="sql-droptablespace-title">
+ command.
+ </para>
- To determine the set of existing tablespaces, examine the
- <structname>pg_tablespace</> system catalog, for example
+ <para>
+ To determine the set of existing tablespaces, examine the
+ <structname>pg_tablespace</> system catalog, for example
<synopsis>
SELECT spcname FROM pg_tablespace;
</synopsis>
- The <xref linkend="app-psql"> program's <literal>\db</> meta-command
- is also useful for listing the existing tablespaces.
- </para>
+ The <xref linkend="app-psql"> program's <literal>\db</> meta-command
+ is also useful for listing the existing tablespaces.
+ </para>
-
<productname>PostgreSQL</> makes use of symbolic links
- to simplify the implementation of tablespaces. This
- means that tablespaces can be used <emphasis>only</> on systems
- that support symbolic links.
- </para>
+ <para>
+ <productname>PostgreSQL</> makes use of symbolic links
+ to simplify the implementation of tablespaces. This
+ means that tablespaces can be used <emphasis>only</> on systems
+ that support symbolic links.
+ </para>
- The directory <filename>$PGDATA/pg_tblspc</> contains symbolic links that
- point to each of the non-built-in tablespaces defined in the cluster.
- Although not recommended, it is possible to adjust the tablespace
- layout by hand by redefining these links. Two warnings: do not do so
- while the server is running; and after you restart the server,
- update the <structname>pg_tablespace</> catalog to show the new
- locations. (If you do not, <literal>pg_dump</> will continue to show
- the old tablespace locations.)
- </para>
+ <para>
+ The directory <filename>$PGDATA/pg_tblspc</> contains symbolic links that
+ point to each of the non-built-in tablespaces defined in the cluster.
+ Although not recommended, it is possible to adjust the tablespace
+ layout by hand by redefining these links. Two warnings: do not do so
+ while the server is running; and after you restart the server,
+ update the <structname>pg_tablespace</> catalog to show the new
+ locations. (If you do not, <literal>pg_dump</> will continue to show
+ the old tablespace locations.)
+ </para>
</sect1>
</chapter>
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