5 Configuration Parameters

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

GASource pages: PDF 52-55Original PDF on GitHub

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In PostgreSQL 15 the following parameters have been changed.

3.3.1 Added parameters

The following parameters have been added.

Parameter name	Description (context)	Default value
allow_in_place_tablespaces	Developer parameters to create a tablespace in the pg_tblspc directory (superuser)	off
archive_library	WAL archive library name (sighup)	-
log_startup_progress_interval	Time before startup process outputs log if the long-running process occurs (sighup)	10s
recovery_prefetch	Whether WAL prefetching is performed during recovery (sighup)	try
recursive_worktable_factor	Multiplier to determine work table size for recursive queries (user)	10
shared_memory_size	The calculated size of main shared memory (internal)	-
shared_memory_size_in_huge_pages	Number of Huge Pages pages used for shared memory (internal)	-
stats_fetch_consistency	Determines the behavior when cumulative statistics are accessed multiple times (user)	cache
wal_decode_buffer_size	Buffer size for WAL decoding (postmaster)	512kB

Table 17 Added parameters

allow_in_place_tablespaces

Tablespaces can be created in a database cluster by setting this parameter to on and specifying an empty string (’’) in the LOCATION clause of the CREATE TABLESPACE statement.

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Example 64 Create In place tablespace

postgres=# SET allow_in_place_tablespaces = on ;
SET
postgres=# CREATE TABLESPACE ts1 LOCATION '' ;
CREATE TABLESPACE
postgres=# \! ls -l data/pg_tblspc/
total 0
drwx------. 3 postgres 29 Oct 14 14:16 17153

3.3.2 Modified Parameters

The following parameters have been changed in terms of setting range and choices.

Parameter name	Changes
compute_query_id	Regress can now be specified as a configuration value. This is used to facilitate regression testing.
dynamic_shared_memory_type The default value on Solaris has changed to “sysv”.	dynamic_shared_memory_type The default value on Solaris has changed to “sysv”.
log_destination	Jsonlog can now be specified as a configuration value to output logs in JSON format. This change will also be backported to PostgreSQL 14.3 and later.
wal_compression	Pglz, lz4, and zstd compression methods can now be specified. The configuration value on is assumed to be pglz.
shared_preload_libraries	Now also processed in single user mode.

Table 18 Modified Parameters

JSON format log file

If jsonlog is specified for the parameter log_destination, the log file will be output in JSON format. The file extension is .json. A file with a .log extension is also created that outputs only some information.

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Example 65 JSON format log file

postgres=> SHOW log_destination ;
 log_destination
-----------------
 jsonlog
(1 row)
postgres=> \! cat postgresql-2022-10-14_141810.json
"timestamp":"2022-10-14
14:18:10.657
JST","pid":14876,"session_id":"6348f112.3a1c","line_num":1,"session_start":"20
22-10-14 14:18:10 JST","txid":0,"error_severity":"LOG","message":"ending log
output to stderr","hint":"Future log output will go to log destination
\"jsonlog\".","backend_type":"postmaster","query_id":0}
{"timestamp":"2022-10-14
14:18:10.657
JST","pid":14876,"session_id":"6348f112.3a1c","line_num":2,"session_start":"20
22-10-14
14:18:10
JST","txid":0,"error_severity":"LOG","message":"starting
PostgreSQL 15.0 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514
(Red Hat 8.5.0-10), 64-bit","backend_type":"postmaster","query_id":0}

3.3.3 Parameters with default values changed

The following parameters have changed default values.

Parametername	PostgreSQL14	PostgreSQL15
hash_mem_multiplier	1.0	2.0
log_autovacuum_min_durationlog_checkpoints	-1	10min
	off	on
server_version	14.5	15.0
server_version_num	140005	150000

Table 19 Parameters with default values changed

3.3.4 Removed parameter

The following parameter have been removed.

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Parameter name	Reason
stats_temp_directory	It was removed due to the shared memory of statistics.

Table 20 Removed parameter

3.3.5 Error when changing parameters

Some extension modules (auto_explain, pg_prewarm, pg_stat_statements, plperl, plpgsql) now generate errors when attempting to set parameters that do not exist after loading the module.

Example 66 Output error

postgres=> CREATE FUNCTION getwork() RETURNS TEXT AS $$
BEGIN
  RETURN current_setting('work_mem') ;
END ;
$$ LANGUAGE plpgsql ;
CREATE FUNCTION
postgres=> SET plpgsql.bad_parameter_name TO false ;
ERROR:  invalid configuration parameter name "plpgsql.bad_parameter_name"
DETAIL:  "plpgsql" is a reserved prefix.