mirror of https://github.com/postgres/postgres
Bruce Momjian
24 years ago
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$Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.1 2002/06/13 05:15:22 momjian Exp $ |
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<chapter id="diskusage"> |
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<title>Monitoring Disk Usage</title> |
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<sect1 id="disk-usage"> |
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<title>Monitoring Disk Usage</Title> |
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<indexterm zone="disk-usage"> |
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<primary>disk usage</primary> |
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</indexterm> |
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<para> |
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Each table has a primary heap disk file where most of the data is |
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stored. To store long column values, there is also a |
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<acronym>TOAST</> file associated with the table, named based on the |
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table's oid (actually pg_class.relfilenode), and an index on the |
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<acronym>TOAST</> table. There also may be indexes associated with |
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the base table. |
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</para> |
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<para> |
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You can monitor disk space from two places; from inside |
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<application>psql</> and from the command line using |
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<application>contrib/oid2name</>. Using <application>psql</> you can |
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issue queries to see the disk usage for any table: |
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<programlisting> |
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play=# SELECT relfilenode, relpages |
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play-# FROM pg_class |
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play-# WHERE relname = 'customer'; |
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relfilenode | relpages |
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-------------+---------- |
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16806 | 60 |
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(1 row) |
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</programlisting> |
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</para> |
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<para> |
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Each page is typically 8 kilobytes. <literal>relpages</> is only |
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updated by <command>VACUUM</> and <command>ANALYZE</>. To show the |
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space used by <acronym>TOAST</> tables, use a query based on the heap |
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relfilenode: |
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<programlisting> |
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play=# SELECT relname, relpages |
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play-# FROM pg_class |
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play-# WHERE relname = 'pg_toast_16806' or |
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play-# relname = 'pg_toast_16806_index' |
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play-# ORDER BY relname; |
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relname | relpages |
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----------------------+---------- |
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pg_toast_16806 | 0 |
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pg_toast_16806_index | 1 |
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</programlisting> |
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</para> |
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<para> |
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You can easily display index usage too: |
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<programlisting> |
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play=# SELECT c2.relname, c2.relpages |
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play-# FROM pg_class c, pg_class c2, pg_index i |
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play-# WHERE c.relname = 'customer' AND |
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play-# c.oid = i.indrelid AND |
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play-# c2.oid = i.indexrelid |
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play-# ORDER BY c2.relname; |
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relname | relpages |
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----------------------+---------- |
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customer_id_indexdex | 26 |
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</programlisting> |
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</para> |
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<para> |
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It is easy to find your largest files using <application>psql</>: |
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<programlisting> |
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play=# SELECT relname, relpages |
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play-# FROM pg_class |
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play-# ORDER BY relpages DESC; |
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relname | relpages |
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----------------------+---------- |
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bigtable | 3290 |
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customer | 3144 |
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</programlisting> |
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</para> |
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<para> |
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You can also use <application>oid2name</> to show disk usage. See |
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<filename>README.oid2name</> for examples. It includes a script |
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shows disk usage for each database. |
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</para> |
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</sect1> |
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</chapter> |
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<!-- Keep this comment at the end of the file |
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Local variables: |
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mode:sgml |
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sgml-omittag:nil |
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sgml-shorttag:t |
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sgml-minimize-attributes:nil |
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sgml-always-quote-attributes:t |
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sgml-indent-step:1 |
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sgml-indent-data:t |
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sgml-parent-document:nil |
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sgml-default-dtd-file:"./reference.ced" |
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sgml-exposed-tags:nil |
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sgml-local-catalogs:("/usr/lib/sgml/catalog") |
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sgml-local-ecat-files:nil |
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End: |
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--> |
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@ -1,9 +0,0 @@ |
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<Chapter Id="storage"> |
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<Title>Disk Storage</Title> |
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<Para> |
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This section needs to be written. Some information is in the FAQ. Volunteers? |
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- thomas 1998-01-11 |
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</Para> |
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</Chapter> |
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