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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 13:44:03 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 13:44:03 +0000
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postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.zip
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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>29.1. Determining Disk Usage</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="diskusage.html" title="Chapter 29. Monitoring Disk Usage" /><link rel="next" href="disk-full.html" title="29.2. Disk Full Failure" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">29.1. Determining Disk Usage</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="diskusage.html" title="Chapter 29. Monitoring Disk Usage">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="diskusage.html" title="Chapter 29. Monitoring Disk Usage">Up</a></td><th width="60%" align="center">Chapter 29. Monitoring Disk Usage</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="disk-full.html" title="29.2. Disk Full Failure">Next</a></td></tr></table><hr /></div><div class="sect1" id="DISK-USAGE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">29.1. Determining Disk Usage <a href="#DISK-USAGE" class="id_link">#</a></h2></div></div></div><a id="id-1.6.16.3.2" class="indexterm"></a><p>
+ Each table has a primary heap disk file where most of the data is
+ stored. If the table has any columns with potentially-wide values,
+ there also might be a <acronym class="acronym">TOAST</acronym> file associated with the table,
+ which is used to store values too wide to fit comfortably in the main
+ table (see <a class="xref" href="storage-toast.html" title="73.2. TOAST">Section 73.2</a>). There will be one valid index
+ on the <acronym class="acronym">TOAST</acronym> table, if present. There also might be indexes
+ associated with the base table. Each table and index is stored in a
+ separate disk file — possibly more than one file, if the file would
+ exceed one gigabyte. Naming conventions for these files are described
+ in <a class="xref" href="storage-file-layout.html" title="73.1. Database File Layout">Section 73.1</a>.
+ </p><p>
+ You can monitor disk space in three ways:
+ using the SQL functions listed in <a class="xref" href="functions-admin.html#FUNCTIONS-ADMIN-DBSIZE" title="Table 9.96. Database Object Size Functions">Table 9.96</a>,
+ using the <a class="xref" href="oid2name.html" title="oid2name"><span class="refentrytitle">oid2name</span></a> module, or
+ using manual inspection of the system catalogs.
+ The SQL functions are the easiest to use and are generally recommended.
+ The remainder of this section shows how to do it by inspection of the
+ system catalogs.
+ </p><p>
+ Using <span class="application">psql</span> on a recently vacuumed or analyzed database,
+ you can issue queries to see the disk usage of any table:
+</p><pre class="programlisting">
+SELECT pg_relation_filepath(oid), relpages FROM pg_class WHERE relname = 'customer';
+
+ pg_relation_filepath | relpages
+----------------------+----------
+ base/16384/16806 | 60
+(1 row)
+</pre><p>
+ Each page is typically 8 kilobytes. (Remember, <code class="structfield">relpages</code>
+ is only updated by <code class="command">VACUUM</code>, <code class="command">ANALYZE</code>, and
+ a few DDL commands such as <code class="command">CREATE INDEX</code>.) The file path name
+ is of interest if you want to examine the table's disk file directly.
+ </p><p>
+ To show the space used by <acronym class="acronym">TOAST</acronym> tables, use a query
+ like the following:
+</p><pre class="programlisting">
+SELECT relname, relpages
+FROM pg_class,
+ (SELECT reltoastrelid
+ FROM pg_class
+ WHERE relname = 'customer') AS ss
+WHERE oid = ss.reltoastrelid OR
+ oid = (SELECT indexrelid
+ FROM pg_index
+ WHERE indrelid = ss.reltoastrelid)
+ORDER BY relname;
+
+ relname | relpages
+----------------------+----------
+ pg_toast_16806 | 0
+ pg_toast_16806_index | 1
+</pre><p>
+ </p><p>
+ You can easily display index sizes, too:
+</p><pre class="programlisting">
+SELECT c2.relname, c2.relpages
+FROM pg_class c, pg_class c2, pg_index i
+WHERE c.relname = 'customer' AND
+ c.oid = i.indrelid AND
+ c2.oid = i.indexrelid
+ORDER BY c2.relname;
+
+ relname | relpages
+-------------------+----------
+ customer_id_index | 26
+</pre><p>
+ </p><p>
+ It is easy to find your largest tables and indexes using this
+ information:
+</p><pre class="programlisting">
+SELECT relname, relpages
+FROM pg_class
+ORDER BY relpages DESC;
+
+ relname | relpages
+----------------------+----------
+ bigtable | 3290
+ customer | 3144
+</pre><p>
+ </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="diskusage.html" title="Chapter 29. Monitoring Disk Usage">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="diskusage.html" title="Chapter 29. Monitoring Disk Usage">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="disk-full.html" title="29.2. Disk Full Failure">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 29. Monitoring Disk Usage </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 29.2. Disk Full Failure</td></tr></table></div></body></html> \ No newline at end of file
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