PostgreSQL 15 → 16 GUC diff

Core configuration parameters added, removed, or changed in boot default between PostgreSQL 15 and 16.

Note

Fact. The measured inventory changes from 355 to 364 settings: 14 added, 2 boot-default changes, and 5 removed.

Added parameters

Parameter	Type	Context	Boot default	Category
`createrole_self_grant`	`string`	`user`	`""` (empty string)	Client Connection Defaults / Statement Behavior
`debug_io_direct`	`string`	`postmaster`	`""` (empty string)	Developer Options
`debug_logical_replication_streaming`	`enum`	`user`	`buffered`	Developer Options
`debug_parallel_query`	`enum`	`user`	`off`	Developer Options
`enable_presorted_aggregate`	`bool`	`user`	`on`	Query Tuning / Planner Method Configuration
`file_extend_method`	`enum`	`sighup`	`posix_fallocate`	Resource Usage / Disk
`gss_accept_delegation`	`bool`	`sighup`	`off`	Connections and Authentication / Authentication
`icu_validation_level`	`enum`	`user`	`warning`	Client Connection Defaults / Locale and Formatting
`max_parallel_apply_workers_per_subscription`	`integer`	`sighup`	`2`	Replication / Subscribers
`reserved_connections`	`integer`	`postmaster`	`0`	Connections and Authentication / Connection Settings
`scram_iterations`	`integer`	`user`	`4096`	Connections and Authentication / Authentication
`send_abort_for_crash`	`bool`	`sighup`	`off`	Developer Options
`send_abort_for_kill`	`bool`	`sighup`	`off`	Developer Options
`vacuum_buffer_usage_limit`	`integer`	`user`	`256 kB` (256 KiB)	Resource Usage / Memory

Boot-default changes

Parameter	PG15	PG16	Category
`server_version`	`15.19 (Debian 15.19-1.pgdg13+2)`	`16.15 (Debian 16.15-1.pgdg13+2)`	Preset Options
`server_version_num`	`150019`	`160015`	Preset Options

Removed parameters

Parameter	Last type	Context	Last boot default	Category
`force_parallel_mode`	`enum`	`user`	`off`	Developer Options
`lc_collate`	`string`	`internal`	`C`	Preset Options
`lc_ctype`	`string`	`internal`	`C`	Preset Options
`promote_trigger_file`	`string`	`sighup`	`""` (empty string)	Replication / Standby Servers
`vacuum_defer_cleanup_age`	`integer`	`sighup`	`0`	Replication / Primary Server

Method

The three lists compare the pinned PG15 and PG16 pg_settings snapshots directly. A default change is a change in the boot_val plus unit pair; setting is excluded so an initdb-generated value is not mistaken for the compiled boot default.