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<html>
<head>
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<title>9.20.System Administration Functions</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="functions-admin"></a>9.20.System Administration Functions</h2></div></div></div>
<p> <a href="functions-admin.html#functions-admin-set-table" title="Table9.44.Configuration Settings Functions">Table9.44, “Configuration Settings Functions”</a> shows the functions
available to query and alter run-time configuration parameters.
</p>
<div class="table">
<a name="functions-admin-set-table"></a><p class="title"><b>Table9.44.Configuration Settings Functions</b></p>
<div class="table-contents"><table summary="Configuration Settings Functions" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Return Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td> <code class="literal"><code class="function">current_setting</code>(<em class="parameter"><code>setting_name</code></em>)</code>
</td>
<td><code class="type">text</code></td>
<td>current value of setting</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">set_config(<em class="parameter"><code>setting_name</code></em>, ,
<em class="parameter"><code>new_value</code></em>, ,
<em class="parameter"><code>is_local</code></em>)</code></code>
</td>
<td><code class="type">text</code></td>
<td>set parameter and return new value</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><a name="id624629"></a><a name="id624640"></a><a name="id624650"></a><p> The function <code class="function">current_setting</code> yields the
current value of the setting <em class="parameter"><code>setting_name</code></em>.
It corresponds to the <acronym class="acronym">SQL</acronym> command
<code class="command">SHOW</code>. An example:
</p>
<pre class="programlisting">SELECT current_setting('datestyle');
current_setting
-----------------
ISO, MDY
(1 row)</pre>
<p>
</p>
<p> <code class="function">set_config</code> sets the parameter
<em class="parameter"><code>setting_name</code></em> to
<em class="parameter"><code>new_value</code></em>. If
<em class="parameter"><code>is_local</code></em> is <code class="literal">true</code>, the
new value will only apply to the current transaction. If you want
the new value to apply for the current session, use
<code class="literal">false</code> instead. The function corresponds to the
SQL command <code class="command">SET</code>. An example:
</p>
<pre class="programlisting">SELECT set_config('log_statement_stats', 'off', false);
set_config
------------
off
(1 row)</pre>
<p>
</p>
<a name="id624764"></a><a name="id624775"></a><a name="id624785"></a><a name="id624796"></a><p> The functions shown in <a href="functions-admin.html#functions-admin-signal-table" title="Table9.45.Server Signalling Functions">Table9.45, “Server Signalling Functions”</a> send control signals to
other server processes. Use of these functions is restricted
to superusers.
</p>
<div class="table">
<a name="functions-admin-signal-table"></a><p class="title"><b>Table9.45.Server Signalling Functions</b></p>
<div class="table-contents"><table summary="Server Signalling Functions" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Return Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td> <code class="literal"><code class="function">pg_cancel_backend</code>(<em class="parameter"><code>pid</code></em> <code class="type">int</code>)</code>
</td>
<td><code class="type">boolean</code></td>
<td>Cancel a backend's current query</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_reload_conf</code>()</code>
</td>
<td><code class="type">boolean</code></td>
<td>Cause server processes to reload their configuration files</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_rotate_logfile</code>()</code>
</td>
<td><code class="type">boolean</code></td>
<td>Rotate server's log file</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p> Each of these functions returns <code class="literal">true</code> if
successful and <code class="literal">false</code> otherwise.
</p>
<p> <code class="function">pg_cancel_backend</code> sends a query cancel
(<span class="systemitem">SIGINT</span>) signal to a backend process identified by
process ID. The process ID of an active backend can be found from
the <code class="structfield">procpid</code> column in the
<code class="structname">pg_stat_activity</code> view, or by listing the
<code class="command">postgres</code> processes on the server with
<span class="application">ps</span>.
</p>
<p> <code class="function">pg_reload_conf</code> sends a <span class="systemitem">SIGHUP</span> signal
to the <span class="application">postmaster</span>, causing the configuration files
to be reloaded by all server processes.
</p>
<p> <code class="function">pg_rotate_logfile</code> signals the log-file manager to switch
to a new output file immediately. This works only when
<code class="varname">redirect_stderr</code> is used for logging, since otherwise there
is no log-file manager subprocess.
</p>
<a name="id625022"></a><a name="id625032"></a><a name="id625043"></a><p> The functions shown in <a href="functions-admin.html#functions-admin-backup-table" title="Table9.46.Backup Control Functions">Table9.46, “Backup Control Functions”</a> assist in making on-line backups.
Use of these functions is restricted to superusers.
</p>
<div class="table">
<a name="functions-admin-backup-table"></a><p class="title"><b>Table9.46.Backup Control Functions</b></p>
<div class="table-contents"><table summary="Backup Control Functions" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Return Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td> <code class="literal"><code class="function">pg_start_backup</code>(<em class="parameter"><code>label</code></em> <code class="type">text</code>)</code>
</td>
<td><code class="type">text</code></td>
<td>Set up for performing on-line backup</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_stop_backup</code>()</code>
</td>
<td><code class="type">text</code></td>
<td>Finish performing on-line backup</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p> <code class="function">pg_start_backup</code> accepts a single parameter which is an
arbitrary user-defined label for the backup. (Typically this would be
the name under which the backup dump file will be stored.) The function
writes a backup label file into the database cluster's data directory,
and then returns the backup's starting WAL offset as text. (The user
need not pay any attention to this result value, but it is provided in
case it is of use.)
</p>
<p> <code class="function">pg_stop_backup</code> removes the label file created by
<code class="function">pg_start_backup</code>, and instead creates a backup history file in
the WAL archive area. The history file includes the label given to
<code class="function">pg_start_backup</code>, the starting and ending WAL offsets for
the backup, and the starting and ending times of the backup. The return
value is the backup's ending WAL offset (which again may be of little
interest).
</p>
<p> For details about proper usage of these functions, see
<a href="backup-online.html" title="23.3.On-line backup and point-in-time recovery (PITR)">Section23.3, “On-line backup and point-in-time recovery (PITR)”</a>.
</p>
<p> The functions shown in <a href="functions-admin.html#functions-admin-dbsize" title="Table9.47.Database Object Size Functions">Table9.47, “Database Object Size Functions”</a> calculate
the actual disk space usage of database objects.
</p>
<a name="id625213"></a><a name="id625223"></a><a name="id625234"></a><a name="id625244"></a><a name="id625255"></a><a name="id625265"></a><div class="table">
<a name="functions-admin-dbsize"></a><p class="title"><b>Table9.47.Database Object Size Functions</b></p>
<div class="table-contents"><table summary="Database Object Size Functions" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Return Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td>
<code class="function">pg_column_size</code>(<code class="type">any</code>)</td>
<td><code class="type">int</code></td>
<td>Number of bytes used to store a particular value (possibly compressed)</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_tablespace_size</code>(<code class="type">oid</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td>Disk space used by the tablespace with the specified OID</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_tablespace_size</code>(<code class="type">name</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td>Disk space used by the tablespace with the specified name</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_database_size</code>(<code class="type">oid</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td>Disk space used by the database with the specified OID</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_database_size</code>(<code class="type">name</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td>Disk space used by the database with the specified name</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_relation_size</code>(<code class="type">oid</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td>Disk space used by the table or index with the specified OID</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_relation_size</code>(<code class="type">text</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td> Disk space used by the table or index with the specified name.
The table name may be qualified with a schema name
</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_total_relation_size</code>(<code class="type">oid</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td> Total disk space used by the table with the specified OID,
including indexes and toasted data
</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_total_relation_size</code>(<code class="type">text</code>)</code>
</td>
<td><code class="type">bigint</code></td>
<td> Total disk space used by the table with the specified name,
including indexes and toasted data. The table name may be
qualified with a schema name
</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_size_pretty</code>(<code class="type">bigint</code>)</code>
</td>
<td><code class="type">text</code></td>
<td>Converts a size in bytes into a human-readable format with size units</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p> <code class="function">pg_column_size</code> shows the space used to store any individual
data value.
</p>
<p> <code class="function">pg_tablespace_size</code> and <code class="function">pg_database_size</code> accept
the OID or name of a tablespace or database, and return the total disk
space used therein.
</p>
<p> <code class="function">pg_relation_size</code> accepts the OID or name of a table, index or
toast table, and returns the size in bytes.
</p>
<p> <code class="function">pg_total_relation_size</code> accepts the OID or name of a
table or toast table, and returns the size in bytes of the data
and all associated indexes and toast tables.
</p>
<p> <code class="function">pg_size_pretty</code> can be used to format the result of one of
the other functions in a human-readable way, using kB, MB, GB or TB as
appropriate.
</p>
<p> The functions shown in <a href="functions-admin.html#functions-admin-genfile" title="Table9.48.Generic File Access Functions">Table9.48, “Generic File Access Functions”</a> provide native file access to
files on the machine hosting the server. Only files within the
database cluster directory and the <code class="varname">log_directory</code> may be
accessed. Use a relative path for files within the cluster directory,
and a path matching the <code class="varname">log_directory</code> configuration setting
for log files. Use of these functions is restricted to superusers.
</p>
<div class="table">
<a name="functions-admin-genfile"></a><p class="title"><b>Table9.48.Generic File Access Functions</b></p>
<div class="table-contents"><table summary="Generic File Access Functions" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Return Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td> <code class="literal"><code class="function">pg_ls_dir</code>(<em class="parameter"><code>dirname</code></em> <code class="type">text</code>)</code>
</td>
<td><code class="type">setof text</code></td>
<td>List the contents of a directory</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_read_file</code>(<em class="parameter"><code>filename</code></em> <code class="type">text</code>, <em class="parameter"><code>offset</code></em> <code class="type">bigint</code>, <em class="parameter"><code>length</code></em> <code class="type">bigint</code>)</code>
</td>
<td><code class="type">text</code></td>
<td>Return the contents of a text file</td>
</tr>
<tr>
<td> <code class="literal"><code class="function">pg_stat_file</code>(<em class="parameter"><code>filename</code></em> <code class="type">text</code>)</code>
</td>
<td><code class="type">record</code></td>
<td>Return information about a file</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><a name="id625785"></a><p> <code class="function">pg_ls_dir</code> returns all the names in the specified
directory, except the special entries “<span class="quote"><code class="literal">.</code></span>” and
“<span class="quote"><code class="literal">..</code></span>”.
</p>
<a name="id625820"></a><p> <code class="function">pg_read_file</code> returns part of a text file, starting
at the given <em class="parameter"><code>offset</code></em>, returning at most <em class="parameter"><code>length</code></em>
bytes (less if the end of file is reached first). If <em class="parameter"><code>offset</code></em>
is negative, it is relative to the end of the file.
</p>
<a name="id625862"></a><p> <code class="function">pg_stat_file</code> returns a record containing the file
size, last accessed time stamp, last modified time stamp,
last file status change time stamp (Unix platforms only),
file creation timestamp (Windows only), and a <code class="type">boolean</code> indicating
if it is a directory. Typical usages include:
</p>
<pre class="programlisting">SELECT * FROM pg_stat_file('filename');
SELECT (pg_stat_file('filename')).modification;</pre>
<p>
</p>
</div></body>
</html>
|
