Postgresql 中文操作指南

54.24. pg_settings #

视图 pg_settings 提供对服务器运行时参数的访问权限。它基本上是 SHOW 和 SET 命令的备用接口。它还可访问 SHOW 直接不可获取的每个参数的一些事实，例如最小值和最大值。

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

Table 54.24. pg_settings Columns

Column Type

Description

name text

Run-time configuration parameter name

setting text

Current value of the parameter

unit text

Implicit unit of the parameter

category text

Logical group of the parameter

short_desc text

A brief description of the parameter

extra_desc text

Additional, more detailed, description of the parameter

context text

Context required to set the parameter’s value (see below)

vartype text

Parameter type (bool, enum, integer, real, or string)

source text

Source of the current parameter value

min_val text

Minimum allowed value of the parameter (null for non-numeric values)

max_val text

Maximum allowed value of the parameter (null for non-numeric values)

enumvals text[]

Allowed values of an enum parameter (null for non-enum values)

boot_val text

Parameter value assumed at server startup if the parameter is not otherwise set

reset_val text

Value that RESET would reset the parameter to in the current session

sourcefile text

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 pg_read_all_settings); helpful when using include directives in configuration files

sourceline int4

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 pg_read_all_settings).

pending_restart bool

true if the value has been changed in the configuration file but needs a restart; or false otherwise.

context 有几种可能的值。按照更改设置的难度递减排列，它们是：

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.

有关更改这些参数的多种方式的详细信息，请参见 Section 20.1 。

See Section 20.1 for more information about the various ways to change these parameters.

无法插入或删除此视图，但是可以更新该视图。 对 pg_settings 行应用的 UPDATE SET 等效于对该命名参数执行该命令。更改只影响当前会话使用的值。如果在稍后中止的事务中发出了 UPDATE ，则当事务回滚时， UPDATE 命令的效果就会消失。一旦提交了周围的事务，除非被另一个 UPDATE 或 SET 覆盖，否则效果将持续到会话结束。

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.

此视图不会显示 customized options ，除非定义它们的扩展模块已由执行查询的后端进程加载（例如，通过 shared_preload_libraries 中的说明、调用扩展中的 C 函数或 LOAD 命令）。例如，由于 archive modules 通常只由归档程序进程加载，而不是常规会话，除非采取特殊措施将它们加载到执行查询的后端进程中，否则此视图不会显示此类模块定义的任何自定义选项。

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.