ok
Direktori : /opt/alt/postgresql11/usr/share/doc/alt-postgresql11-9.2.24/html/ |
Current File : //opt/alt/postgresql11/usr/share/doc/alt-postgresql11-9.2.24/html/config-setting.html |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Setting Parameters</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 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Server Configuration" HREF="runtime-config.html"><LINK REL="PREVIOUS" TITLE="Server Configuration" HREF="runtime-config.html"><LINK REL="NEXT" TITLE="File Locations" HREF="runtime-config-file-locations.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="2017-11-06T22:43:11"></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" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Server Configuration" HREF="runtime-config.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="runtime-config.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 18. Server Configuration</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="File Locations" HREF="runtime-config-file-locations.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="CONFIG-SETTING" >18.1. Setting Parameters</A ></H1 ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="CONFIG-SETTING-NAMES-VALUES" >18.1.1. Parameter Names and Values</A ></H2 ><P > All parameter names are case-insensitive. Every parameter takes a value of one of five types: Boolean, integer, floating point, string or enum. Boolean values can be written as <TT CLASS="LITERAL" >on</TT >, <TT CLASS="LITERAL" >off</TT >, <TT CLASS="LITERAL" >true</TT >, <TT CLASS="LITERAL" >false</TT >, <TT CLASS="LITERAL" >yes</TT >, <TT CLASS="LITERAL" >no</TT >, <TT CLASS="LITERAL" >1</TT >, <TT CLASS="LITERAL" >0</TT > (all case-insensitive) or any unambiguous prefix of these. </P ><P > Some settings specify a memory or time value. Each of these has an implicit unit, which is either kilobytes, blocks (typically eight kilobytes), milliseconds, seconds, or minutes. Default units can be found by referencing <TT CLASS="STRUCTNAME" >pg_settings</TT >.<TT CLASS="STRUCTFIELD" >unit</TT >. For convenience, a different unit can also be specified explicitly. Valid memory units are <TT CLASS="LITERAL" >kB</TT > (kilobytes), <TT CLASS="LITERAL" >MB</TT > (megabytes), and <TT CLASS="LITERAL" >GB</TT > (gigabytes); valid time units are <TT CLASS="LITERAL" >ms</TT > (milliseconds), <TT CLASS="LITERAL" >s</TT > (seconds), <TT CLASS="LITERAL" >min</TT > (minutes), <TT CLASS="LITERAL" >h</TT > (hours), and <TT CLASS="LITERAL" >d</TT > (days). Note that the multiplier for memory units is 1024, not 1000. </P ><P > Parameters of type <SPAN CLASS="QUOTE" >"enum"</SPAN > are specified in the same way as string parameters, but are restricted to a limited set of values. The allowed values can be found from <TT CLASS="STRUCTNAME" >pg_settings</TT >.<TT CLASS="STRUCTFIELD" >enumvals</TT >. Enum parameter values are case-insensitive. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="CONFIG-SETTING-CONFIGURATION-FILE" >18.1.2. Setting Parameters via the Configuration File</A ></H2 ><P > One way to set these parameters is to edit the file <TT CLASS="FILENAME" >postgresql.conf</TT >, which is normally kept in the data directory. (A default copy is installed there when the database cluster directory is initialized.) An example of what this file might look like is: </P><PRE CLASS="PROGRAMLISTING" ># This is a comment log_connections = yes log_destination = 'syslog' search_path = '"$user", public' shared_buffers = 128MB</PRE ><P> One parameter is specified per line. The equal sign between name and value is optional. Whitespace is insignificant and blank lines are ignored. Hash marks (<TT CLASS="LITERAL" >#</TT >) designate the remainder of the line as a comment. Parameter values that are not simple identifiers or numbers must be single-quoted. To embed a single quote in a parameter value, write either two quotes (preferred) or backslash-quote. </P ><P > In addition to parameter settings, the <TT CLASS="FILENAME" >postgresql.conf</TT > file can contain <I CLASS="FIRSTTERM" >include directives</I >, which specify another file to read and process as if it were inserted into the configuration file at this point. This feature allows a configuration file to be divided into physically separate parts. Include directives simply look like: </P><PRE CLASS="PROGRAMLISTING" >include 'filename'</PRE ><P> If the file name is not an absolute path, it is taken as relative to the directory containing the referencing configuration file. Inclusions can be nested. </P ><P > There is also an <TT CLASS="LITERAL" >include_if_exists</TT > directive, which acts the same as the <TT CLASS="LITERAL" >include</TT > directive, except for the behavior when the referenced file does not exist or cannot be read. A regular <TT CLASS="LITERAL" >include</TT > will consider this an error condition, but <TT CLASS="LITERAL" >include_if_exists</TT > merely logs a message and continues processing the referencing configuration file. </P ><P > The configuration file is reread whenever the main server process receives a <SPAN CLASS="SYSTEMITEM" >SIGHUP</SPAN > signal (which is most easily sent by means of <TT CLASS="LITERAL" >pg_ctl reload</TT >). The main server process also propagates this signal to all currently running server processes so that existing sessions also get the new value. Alternatively, you can send the signal to a single server process directly. Some parameters can only be set at server start; any changes to their entries in the configuration file will be ignored until the server is restarted. Invalid parameter settings in the configuration file are likewise ignored (but logged) during <SPAN CLASS="SYSTEMITEM" >SIGHUP</SPAN > processing. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="CONFIG-SETTING-OTHER-METHODS" >18.1.3. Other Ways to Set Parameters</A ></H2 ><P > A second way to set these configuration parameters is to give them as a command-line option to the <TT CLASS="COMMAND" >postgres</TT > command, such as: </P><PRE CLASS="PROGRAMLISTING" >postgres -c log_connections=yes -c log_destination='syslog'</PRE ><P> Command-line options override any conflicting settings in <TT CLASS="FILENAME" >postgresql.conf</TT >. Note that this means you won't be able to change the value on-the-fly by editing <TT CLASS="FILENAME" >postgresql.conf</TT >, so while the command-line method might be convenient, it can cost you flexibility later. </P ><P > Occasionally it is useful to give a command line option to one particular session only. The environment variable <TT CLASS="ENVAR" >PGOPTIONS</TT > can be used for this purpose on the client side: </P><PRE CLASS="PROGRAMLISTING" >env PGOPTIONS='-c geqo=off' psql</PRE ><P> (This works for any <SPAN CLASS="APPLICATION" >libpq</SPAN >-based client application, not just <SPAN CLASS="APPLICATION" >psql</SPAN >.) Note that this won't work for parameters that are fixed when the server is started or that must be specified in <TT CLASS="FILENAME" >postgresql.conf</TT >. </P ><P > Furthermore, it is possible to assign a set of parameter settings to a user or a database. Whenever a session is started, the default settings for the user and database involved are loaded. The commands <A HREF="sql-alterrole.html" >ALTER ROLE</A > and <A HREF="sql-alterdatabase.html" >ALTER DATABASE</A >, respectively, are used to configure these settings. Per-database settings override anything received from the <TT CLASS="COMMAND" >postgres</TT > command-line or the configuration file, and in turn are overridden by per-user settings; both are overridden by per-session settings. </P ><P > Some parameters can be changed in individual <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM > sessions with the <A HREF="sql-set.html" >SET</A > command, for example: </P><PRE CLASS="SCREEN" >SET ENABLE_SEQSCAN TO OFF;</PRE ><P> If <TT CLASS="COMMAND" >SET</TT > is allowed, it overrides all other sources of values for the parameter. Some parameters cannot be changed via <TT CLASS="COMMAND" >SET</TT >: for example, if they control behavior that cannot be changed without restarting the entire <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > server. Also, some parameters require superuser permission to change via <TT CLASS="COMMAND" >SET</TT > or <TT CLASS="COMMAND" >ALTER</TT >. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="CONFIG-SETTING-EXAMINING" >18.1.4. Examining Parameter Settings</A ></H2 ><P > The <A HREF="sql-show.html" >SHOW</A > command allows inspection of the current values of all parameters. </P ><P > The virtual table <TT CLASS="STRUCTNAME" >pg_settings</TT > also allows displaying and updating session run-time parameters; see <A HREF="view-pg-settings.html" >Section 45.64</A > for details and a description of the different variable types and when they can be changed. <TT CLASS="STRUCTNAME" >pg_settings</TT > is equivalent to <TT CLASS="COMMAND" >SHOW</TT > and <TT CLASS="COMMAND" >SET</TT >, but can be more convenient to use because it can be joined with other tables, or selected from using any desired selection condition. It also contains more information about each parameter than is available from <TT CLASS="COMMAND" >SHOW</TT >. </P ></DIV ></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="runtime-config.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="runtime-config-file-locations.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Server Configuration</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="runtime-config.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >File Locations</TD ></TR ></TABLE ></DIV ></BODY ></HTML >