PDF page 52
In PostgreSQL 15 the following parameters have been changed. #### 3.3.1 Added parameters {#pg15-3-3-1-added-parameters} The following parameters have been added. **Table 17.** Added parameters | 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 | ##### allow_in_place_tablespaces {#pg15-p52-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.PDF page 53
**Example 64.** Create In place tablespace ```text 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 {#pg15-3-3-2-modified-parameters} The following parameters have been changed in terms of setting range and choices. **Table 18.** Modified Parameters | 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. | ##### JSON format log file {#pg15-p53-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.PDF page 54
**Example 65.** JSON format log file ```text 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 {#pg15-3-3-3-parameters-with-default-values-changed} The following parameters have changed default values. **Table 19.** Parameters with default values changed | Parametername | PostgreSQL14 | PostgreSQL15 | Note | | --- | --- | --- | --- | | 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 | | #### 3.3.4 Removed parameter {#pg15-3-3-4-removed-parameter} The following parameter have been removed.PDF page 55
**Table 20.** Removed parameter | Parameter name | Reason | | --- | --- | | stats_temp_directory | It was removed due to the shared memory of statistics. | #### 3.3.5 Error when changing parameters {#pg15-3-3-5-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 ```text 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. ```