|
Server : Apache/2.2.2 (Fedora) System : Linux App1.pathumtani.go.th 2.6.20-1.2320.fc5smp #1 SMP Tue Jun 12 19:40:16 EDT 2007 i686 User : apache ( 48) PHP Version : 5.2.9 Disable Function : NONE Directory : /proc/self/root/usr/share/doc/postgresql-8.1.9/html/ |
Upload File : |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>System Administration Functions</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 8.1.9 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Functions and Operators"
HREF="functions.html"><LINK
REL="PREVIOUS"
TITLE="System Information Functions"
HREF="functions-info.html"><LINK
REL="NEXT"
TITLE="Type Conversion"
HREF="typeconv.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2007-04-20T04:40:08"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="5"
ALIGN="center"
VALIGN="bottom"
>PostgreSQL 8.1.9 Documentation</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="functions-info.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="functions.html"
>Fast Backward</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
>Chapter 9. Functions and Operators</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="top"
><A
HREF="functions.html"
>Fast Forward</A
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="top"
><A
HREF="typeconv.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="FUNCTIONS-ADMIN"
>9.20. System Administration Functions</A
></H1
><P
> <A
HREF="functions-admin.html#FUNCTIONS-ADMIN-SET-TABLE"
>Table 9-44</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
><B
>Table 9-44. Configuration Settings Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>current_setting</CODE
>(<TT
CLASS="PARAMETER"
>setting_name</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>current value of setting</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>set_config(<TT
CLASS="PARAMETER"
>setting_name</TT
>,
<TT
CLASS="PARAMETER"
>new_value</TT
>,
<TT
CLASS="PARAMETER"
>is_local</TT
>)</CODE
></TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>set parameter and return new value</TD
></TR
></TBODY
></TABLE
></DIV
><A
NAME="AEN14266"
></A
><A
NAME="AEN14268"
></A
><A
NAME="AEN14270"
></A
><P
> The function <CODE
CLASS="FUNCTION"
>current_setting</CODE
> yields the
current value of the setting <TT
CLASS="PARAMETER"
>setting_name</TT
>.
It corresponds to the <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> command
<TT
CLASS="COMMAND"
>SHOW</TT
>. 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
<TT
CLASS="PARAMETER"
>setting_name</TT
> to
<TT
CLASS="PARAMETER"
>new_value</TT
>. If
<TT
CLASS="PARAMETER"
>is_local</TT
> is <TT
CLASS="LITERAL"
>true</TT
>, the
new value will only apply to the current transaction. If you want
the new value to apply for the current session, use
<TT
CLASS="LITERAL"
>false</TT
> instead. The function corresponds to the
SQL command <TT
CLASS="COMMAND"
>SET</TT
>. An example:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT set_config('log_statement_stats', 'off', false);
set_config
------------
off
(1 row)</PRE
><P>
</P
><A
NAME="AEN14289"
></A
><A
NAME="AEN14291"
></A
><A
NAME="AEN14293"
></A
><A
NAME="AEN14295"
></A
><P
> The functions shown in <A
HREF="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL-TABLE"
>Table 9-45</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
><B
>Table 9-45. Server Signalling Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_cancel_backend</CODE
>(<TT
CLASS="PARAMETER"
>pid</TT
> <TT
CLASS="TYPE"
>int</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>Cancel a backend's current query</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_reload_conf</CODE
>()</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>Cause server processes to reload their configuration files</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_rotate_logfile</CODE
>()</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>Rotate server's log file</TD
></TR
></TBODY
></TABLE
></DIV
><P
> Each of these functions returns <TT
CLASS="LITERAL"
>true</TT
> if
successful and <TT
CLASS="LITERAL"
>false</TT
> 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 <TT
CLASS="STRUCTFIELD"
>procpid</TT
> column in the
<TT
CLASS="STRUCTNAME"
>pg_stat_activity</TT
> view, or by listing the
<TT
CLASS="COMMAND"
>postgres</TT
> 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
<TT
CLASS="VARNAME"
>redirect_stderr</TT
> is used for logging, since otherwise there
is no log-file manager subprocess.
</P
><A
NAME="AEN14349"
></A
><A
NAME="AEN14351"
></A
><A
NAME="AEN14353"
></A
><P
> The functions shown in <A
HREF="functions-admin.html#FUNCTIONS-ADMIN-BACKUP-TABLE"
>Table 9-46</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
><B
>Table 9-46. Backup Control Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_start_backup</CODE
>(<TT
CLASS="PARAMETER"
>label</TT
> <TT
CLASS="TYPE"
>text</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>Set up for performing on-line backup</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_stop_backup</CODE
>()</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>Finish performing on-line backup</TD
></TR
></TBODY
></TABLE
></DIV
><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"
>Section 23.3</A
>.
</P
><P
> The functions shown in <A
HREF="functions-admin.html#FUNCTIONS-ADMIN-DBSIZE"
>Table 9-47</A
> calculate
the actual disk space usage of database objects.
</P
><A
NAME="AEN14392"
></A
><A
NAME="AEN14394"
></A
><A
NAME="AEN14396"
></A
><A
NAME="AEN14398"
></A
><A
NAME="AEN14400"
></A
><A
NAME="AEN14402"
></A
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-ADMIN-DBSIZE"
></A
><P
><B
>Table 9-47. Database Object Size Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><CODE
CLASS="FUNCTION"
>pg_column_size</CODE
>(<TT
CLASS="TYPE"
>any</TT
>)</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>Number of bytes used to store a particular value (possibly compressed)</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_tablespace_size</CODE
>(<TT
CLASS="TYPE"
>oid</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>Disk space used by the tablespace with the specified OID</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_tablespace_size</CODE
>(<TT
CLASS="TYPE"
>name</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>Disk space used by the tablespace with the specified name</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_database_size</CODE
>(<TT
CLASS="TYPE"
>oid</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>Disk space used by the database with the specified OID</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_database_size</CODE
>(<TT
CLASS="TYPE"
>name</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>Disk space used by the database with the specified name</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_relation_size</CODE
>(<TT
CLASS="TYPE"
>oid</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>Disk space used by the table or index with the specified OID</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_relation_size</CODE
>(<TT
CLASS="TYPE"
>text</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></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
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_total_relation_size</CODE
>(<TT
CLASS="TYPE"
>oid</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
> Total disk space used by the table with the specified OID,
including indexes and toasted data
</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_total_relation_size</CODE
>(<TT
CLASS="TYPE"
>text</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></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
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_size_pretty</CODE
>(<TT
CLASS="TYPE"
>bigint</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>Converts a size in bytes into a human-readable format with size units</TD
></TR
></TBODY
></TABLE
></DIV
><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"
>Table 9-48</A
> provide native file access to
files on the machine hosting the server. Only files within the
database cluster directory and the <TT
CLASS="VARNAME"
>log_directory</TT
> may be
accessed. Use a relative path for files within the cluster directory,
and a path matching the <TT
CLASS="VARNAME"
>log_directory</TT
> configuration setting
for log files. Use of these functions is restricted to superusers.
</P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-ADMIN-GENFILE"
></A
><P
><B
>Table 9-48. Generic File Access Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_ls_dir</CODE
>(<TT
CLASS="PARAMETER"
>dirname</TT
> <TT
CLASS="TYPE"
>text</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>setof text</TT
></TD
><TD
>List the contents of a directory</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_read_file</CODE
>(<TT
CLASS="PARAMETER"
>filename</TT
> <TT
CLASS="TYPE"
>text</TT
>, <TT
CLASS="PARAMETER"
>offset</TT
> <TT
CLASS="TYPE"
>bigint</TT
>, <TT
CLASS="PARAMETER"
>length</TT
> <TT
CLASS="TYPE"
>bigint</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>Return the contents of a text file</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_stat_file</CODE
>(<TT
CLASS="PARAMETER"
>filename</TT
> <TT
CLASS="TYPE"
>text</TT
>)</TT
>
</TD
><TD
><TT
CLASS="TYPE"
>record</TT
></TD
><TD
>Return information about a file</TD
></TR
></TBODY
></TABLE
></DIV
><A
NAME="AEN14547"
></A
><P
> <CODE
CLASS="FUNCTION"
>pg_ls_dir</CODE
> returns all the names in the specified
directory, except the special entries <SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>.</TT
>"</SPAN
> and
<SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>..</TT
>"</SPAN
>.
</P
><A
NAME="AEN14555"
></A
><P
> <CODE
CLASS="FUNCTION"
>pg_read_file</CODE
> returns part of a text file, starting
at the given <TT
CLASS="PARAMETER"
>offset</TT
>, returning at most <TT
CLASS="PARAMETER"
>length</TT
>
bytes (less if the end of file is reached first). If <TT
CLASS="PARAMETER"
>offset</TT
>
is negative, it is relative to the end of the file.
</P
><A
NAME="AEN14562"
></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 <TT
CLASS="TYPE"
>boolean</TT
> 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
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="functions-info.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="typeconv.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>System Information Functions</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="functions.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Type Conversion</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>