5 Configuration Parameters

Added, modified, removed, and default-value changes for configuration parameters.

GASource pages: PDF 77-81Original PDF on GitHub

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In PostgreSQL 17, the following parameters have been changed.

3.3.1 Added parameters

The following parameters have been added. [7750fef, a14354c ,2cdf131, 174c480, 0452b46, 51efe38, 53c2a97, bf279dd, d3ae2a2, 210622c, 705843d]

Parameter name	Description (context)	Default value
allow_alter_system	Allow execution of ALTER SYSTEM statement (sighup)	on
commit_timestamp_buffers	Commit timestamp cache size (postmaster)	0 (auto)
enable_group_by_reordering	GROUP BY replacement optimization (user)	on
event_triggers	Enable event triggers (superuser)	on
huge_pages_status	Indicate whether Huge Pages are being used (internal)	-
io_combine_limit	Maximum number of Raad/Write blocks (user)	128kB
max_notify_queue_pages	Maximum number of pages allocated to NOTIFY/LISTEN queue (postmaster)	1048576
multixact_member_buffers	Member cache size for multi-transaction (postmaster)	32
multixact_offset_buffers	Multi-transaction offset cache size (postmaster)	16
notify_buffers	LISTEN/NOTIFY message cache size (postmaster)	16
restrict_nonsystem_relation_kind	The type of non-system relation to restrict use (user)
serializable_buffers	Serializable transaction cache size (postmaster)	32
synchronized_standby_slots	Replication slot name for standby database (sighup)	''
subtransaction_buffers	Size of sub-transaction cache (postmaster)	0 (auto)
summarize_wal	Output WAL summary (sighup)	off
sync_replication_slots	Whether replication slots are synchronized (sighup)	off
trace_connection_negotiation	Obtain SSL negotiation trace (postmaster)	off
transaction_buffers	Transaction status cache size (postmaster)	0 (auto)
transaction_timeout	Transaction execution timeout (user)	0
wal_summary_keep_time	WAL summary retention duration (sighup)	10d

Table 30 Added parameters

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The restrict_nonsystem_relation_kind will be backported to older versions of PostgreSQL that are supported from PostgreSQL 12 onwards.

Allow_alter_system

This parameter determines whether the ALTER SYSTEM statement is allowed to be executed. The default value is ‘on’, which allows the ALTER SYSTEM statement to be executed. This parameter itself cannot be changed by the ALTER SYSTEM statement.

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Example 84 Permission to execute ALTER SYSTEM statement

postgres=# SHOW allow_alter_system ;
-[ RECORD 1 ]------+----
allow_alter_system | off
postgres=# ALTER SYSTEM SET work_mem='16MB' ;
ERROR:  ALTER SYSTEM is not allowed in this environment
postgres=# SELECT pg_reload_conf() ;
-[ RECORD 1 ]--+--
pg_reload_conf | t
postgres=# SHOW allow_alter_system ;
-[ RECORD 1 ]------+---
allow_alter_system | on
postgres=# ALTER SYSTEM SET allow_alter_system = off ;
ERROR:  parameter "allow_alter_system" cannot be changed

Huge_pages_status

If the parameter huge_pages has the default value (try), no log output will be generated even if the acquisition of Huge Pages fails. The parameter huge_pages_status can be checked to see if the cluster is using Huge Pages.

Value	Description	Note
on	Using Huge Pages
off	Not using Huge Pages
unknown Unknown	unknown Unknown	Only shown in special cases

Table 31 Possible values

Transaction_timeout

Specify the maximum transaction execution time in milliseconds. If a timeout occurs, the session is forcibly disconnected. The default value is 0, which means no timeout will occur.

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Example 85 Transaction timeout

postgres=> SET transaction_timeout = '10s' ;
SET
postgres=> BEGIN ;
BEGIN
postgres=*> SELECT pg_sleep(10) ;
FATAL:  terminating connection due to transaction timeout
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

3.3.2 Modified Parameters

The following parameters have been changed in terms of setting range and choices. [d0c2860, e48b19c, 7c3fb50]

Parameter name	Changes
wal_sync_method	The configuration value fsync_writethrough is no longer available in Microsoft Windows environments.
log_connections	Information on trust connections is now output.
log_replication_commands	Replication slot addition information is now output.
maintenance_work_mem	The minimum has been changed from 1MB to 64kB.

Table 32 Modified Parameters

3.3.3 Parameters with default values changed

The following parameters have changed default values. [98f320e]

Parameter name	PostgreSQL 15	PostgreSQL 16
server_version	16.4	17.0
server_version_num	160004	170000
vacuum_buffer_usage_limit 256kB	vacuum_buffer_usage_limit 256kB	2MB

Table 33 Parameters with default values changed

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3.3.4 Removed parameters

The following parameters have been removed. [884eee5, f691f5b, c7a3e6b]

db_user_namespace	It was removed because it was determined that there were few users.
old_snapshot_threshold	Removed due to accuracy and performance issues. It is a desirable feature, and improved implementations may be available in the future.
trace_recovery_messages	Removed because it can be replaced by pg_waldump command, etc.

Table 34 Removed parameters

Parameter name Reason