log_rotation_size

log_rotation_size is the PostgreSQL setting that defines the maximum size a log file can reach before being rotated.

Note

Fact — official short description: “Sets the maximum size a log file can reach before being rotated.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valuesighup: Takes effect after configuration reload
Unit , ValuekB: Raw unit
Range , Value0 – 2147483647: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueReporting and Logging / Where to Log: Upstream classification
Latest boot value , Value10240: 10 MiB

Lifecycle

Fact	Value
First observed	PG9.0 (research boundary)
Present in	PG9.0–19 Beta 3
Removed in	No
Introduction commit	Not asserted: predates the PG9.0 research boundary
Commit date	—
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.0–19 Beta 3	`10240`	`kB`	10 MiB

How it works

log_rotation_size sets the maximum size a log file can reach before being rotated. 0 disables size-based creation of new log files. The collector rotates when the current file reaches approximately this size; zero disables the size trigger but not time-based rotation.

log_rotation_size is a SIGHUP-context setting: a configuration reload activates the new server value without a restart; subsequent operations that consult it use the refreshed value.

The active path is composed from log_destination, logging_collector or syslog/eventlog, file naming and permissions, rotation triggers, and external shipping or retention.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Use a nonzero log_rotation_size when file size itself must be bounded, and coordinate it with a filename that cannot collide during multiple rotations in one time period. If set to zero, verify that time-based rotation and disk alerts provide the bound instead.
OLAP	Analytical bursts can cross a size threshold repeatedly; test the resulting filename suffixes, shipping throughput, and maximum single-file size rather than choosing a larger number by habit.
Small nodes	A modest size cap limits damage from a logging spike, but too-small files increase metadata and shipping overhead. Zero is acceptable only with a proven time-based cycle and free-space guardrail.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

Template	Effective value	Versus upstream boot	Source expression
OLTP	`0`	different	`'0'`
OLAP	`0`	different	`'0'`
CRIT	`0`	different	`'0'`
TINY	`0`	different	`'0'`

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = 0 (dcs); OLAP: PG9.0–19 Beta 3 = 0 (dcs); CRIT: PG9.0–19 Beta 3 = 0 (dcs); TINY: PG9.0–19 Beta 3 = 0 (dcs). Advice, pending human review — Editorial inference: Disabling size rotation appears intended to make daily time rotation the single file-cycle authority; disk safeguards still need independent verification.

Common pitfalls

Editing log_rotation_size without reloading configuration and verifying the effective value and subsequent behavior.
Combining incompatible destination, collector, filename, and rotation assumptions and then losing or overwriting logs.
Failing to monitor a full or unwritable log target, which can block logging or database activity depending on the path.
Setting zero without a working time-based or external rotation policy and allowing unbounded growth.

logging_collector · log_destination · log_directory · log_filename · log_rotation_age