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Minor improvements to the tablespace documentation.

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Neil Conway 2004-10-29 02:11:18 +00:00
parent ee69be44d5
commit ade8f5c8d4
1 changed files with 28 additions and 27 deletions
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55
doc/src/sgml/manage-ag.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.34 2004/09/30 02:40:23 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.35 2004/10/29 02:11:18 neilc Exp $
-->
<chapter id="managing-databases">
@ -347,21 +347,22 @@ dropdb <replaceable class="parameter">dbname</replaceable>
</para>
<para>
By using tablespaces, a database administrator can control the disk
layout of a <productname>PostgreSQL</> installation. This is useful in
at least two ways. Firstly, if the partition or volume on which the cluster
was initialized runs out of space and cannot be extended logically
or otherwise, a tablespace can be created on a different partition
and used until the system can be reconfigured.
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>
Secondly, tablespaces allow a database administrator to arrange data
locations based on the usage patterns of database objects. For
example, an index which is very heavily used can be placed on 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.
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>
@ -377,14 +378,14 @@ CREATE TABLESPACE fastspace LOCATION '/mnt/sda1/postgresql/data';
</para>
<note>
<para>
There is usually not much point in making more than one
tablespace per logical filesystem, since you can't control the location
of individual files within a logical filesystem. However,
<productname>PostgreSQL</> does not enforce any such limitation, and
indeed it's not directly aware of the filesystem boundaries on your
system. It just stores files in the directories you tell it to use.
</para>
<para>
There is usually not much point in making more than one
tablespace per logical filesystem, since you cannot control the location
of individual files within a logical filesystem. However,
<productname>PostgreSQL</> does not enforce any such limitation, and
indeed it is not directly aware of the filesystem boundaries on your
system. It just stores files in the directories you tell it to use.
</para>
</note>
<para>
@ -416,17 +417,17 @@ CREATE TABLE foo(i int) TABLESPACE space1;
</para>
<para>
A schema does not in itself occupy any storage (other than a system
catalog entry), so assigning a tablespace to a schema does not in itself
do anything. What this actually does is to set a default tablespace
for tables later created within the schema. If
A schema does not in itself occupy any storage (other than a
system catalog entry), so assigning a schema to a tablespace does
not in itself do anything. What this actually does is to set a
default tablespace for tables later created within the schema. If
no tablespace is mentioned when creating a schema, it inherits its
default tablespace from the current database.
</para>
<para>
The default choice of tablespace for an index is the same tablespace
already assigned to the table the index is for.
The default tablespace for an index is the tablespace associated
with the table the index is on.
</para>
<para>