pg_settings
   The view pg_settings provides access to
   run-time parameters of the server.  It is essentially an alternative
   interface to the SHOW
   and SET commands.
   It also provides access to some facts about each parameter that are
   not directly available from SHOW, such as minimum and
   maximum values.
  
Table 51.86. pg_settings Columns
| Column Type Description | 
|---|
| 
        Run-time configuration parameter name | 
| 
        Current value of the parameter | 
| 
        Implicit unit of the parameter | 
| 
        Logical group of the parameter | 
| 
        A brief description of the parameter | 
| 
        Additional, more detailed, description of the parameter | 
| 
        Context required to set the parameter's value (see below) | 
| 
        
       Parameter type ( | 
| 
        Source of the current parameter value | 
| 
        Minimum allowed value of the parameter (null for non-numeric values) | 
| 
        Maximum allowed value of the parameter (null for non-numeric values) | 
| 
        Allowed values of an enum parameter (null for non-enum values) | 
| 
        Parameter value assumed at server startup if the parameter is not otherwise set | 
| 
        
       Value that  | 
| 
        
       Configuration file the current value was set in (null for
       values set from sources other than configuration files, or when
       examined by a user who is neither a superuser or a member of
        | 
| 
        
       Line number within the configuration file the current value was
       set at (null for values set from sources other than configuration files,
       or when examined by a user who is neither a superuser or a member of
        | 
| 
        
        | 
   There are several possible values of context.
   In order of decreasing difficulty of changing the setting, they are:
  
internal
      These settings cannot be changed directly; they reflect internally
      determined values.  Some of them may be adjustable by rebuilding the
      server with different configuration options, or by changing options
      supplied to initdb.
     
postmaster
      These settings can only be applied when the server starts, so any change
      requires restarting the server.  Values for these settings are typically
      stored in the postgresql.conf file, or passed on
      the command line when starting the server.  Of course, settings with any
      of the lower context types can also be
      set at server start time.
     
sighup
      Changes to these settings can be made in
      postgresql.conf without restarting the server.
      Send a SIGHUP signal to the postmaster to
      cause it to re-read postgresql.conf and apply
      the changes.  The postmaster will also forward the
      SIGHUP signal to its child processes so that
      they all pick up the new value.
     
superuser-backend
      Changes to these settings can be made in
      postgresql.conf without restarting the server.
      They can also be set for a particular session in the connection request
      packet (for example, via libpq's PGOPTIONS
      environment variable), but only if the connecting user is a superuser.
      However, these settings never change in a session after it is started.
      If you change them in postgresql.conf, send a
      SIGHUP signal to the postmaster to cause it to
      re-read postgresql.conf.  The new values will only
      affect subsequently-launched sessions.
     
backend
      Changes to these settings can be made in
      postgresql.conf without restarting the server.
      They can also be set for a particular session in the connection request
      packet (for example, via libpq's PGOPTIONS
      environment variable); any user can make such a change for their session.
      However, these settings never change in a session after it is started.
      If you change them in postgresql.conf, send a
      SIGHUP signal to the postmaster to cause it to
      re-read postgresql.conf.  The new values will only
      affect subsequently-launched sessions.
     
superuser
      These settings can be set from postgresql.conf,
      or within a session via the SET command; but only superusers
      can change them via SET.  Changes in
      postgresql.conf will affect existing sessions
      only if no session-local value has been established with SET.
     
user
      These settings can be set from postgresql.conf,
      or within a session via the SET command.  Any user is
      allowed to change their session-local value.  Changes in
      postgresql.conf will affect existing sessions
      only if no session-local value has been established with SET.
     
See Section 19.1 for more information about the various ways to change these parameters.
   The pg_settings view cannot be inserted into or
   deleted from, but it can be updated.  An UPDATE applied
   to a row of pg_settings is equivalent to executing
   the SET command on that named
   parameter. The change only affects the value used by the current
   session. If an UPDATE is issued within a transaction
   that is later aborted, the effects of the UPDATE command
   disappear when the transaction is rolled back. Once the surrounding
   transaction is committed, the effects will persist until the end of the
   session, unless overridden by another UPDATE or
   SET.