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><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="AEN13589"
></A
><A
NAME="AEN13591"
></A
><A
NAME="AEN13593"
></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="AEN13612"
></A
><A
NAME="AEN13614"
></A
><P
> The function shown in <A
HREF="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL-TABLE"
>Table 9-45</A
> sends control signals to
other server processes. Use of this function is restricted
to superusers.
</P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-ADMIN-SIGNAL-TABLE"
></A
><P
><B
>Table 9-45. Backend Signalling Functions</B
></P
><TABLE
BORDER="1"
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><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
>
</TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>Cancel a backend's current query</TD
></TR
></TBODY
></TABLE
></DIV
><P
> This function returns 1 if successful, 0 if not successful.
The process ID (<TT
CLASS="LITERAL"
>pid</TT
>) 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
><A
NAME="AEN13642"
></A
><A
NAME="AEN13644"
></A
><A
NAME="AEN13646"
></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"
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><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_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 22.3</A
>.
</P
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