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 54.24. 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 neither is a superuser nor has privileges 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 neither is a superuser nor has privileges 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
or has been granted the appropriate SET
privilege.
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
and users with the appropriate SET
privilege
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.
This 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
.
This view does not
display customized options
unless the extension module that defines them has been loaded by the
backend process executing the query (e.g., via a mention in
shared_preload_libraries,
a call to a C function in the extension, or the
LOAD
command).
For example, since archive modules
are normally loaded only by the archiver process not regular sessions,
this view will not display any customized options defined by such modules
unless special action is taken to load them into the backend process
executing the query.