# log_directory

> log_directory is the PostgreSQL setting that defines the destination directory for log files.
---

> [!NOTE]
> **Fact — official short description:** “Sets the destination directory for log files.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `string` | Upstream pg_settings type |
| Context | `sighup` | Takes effect after configuration reload |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Reporting and Logging / Where to Log | Upstream classification |
| Latest boot value | `log` | log |
{.fields meta="-"}

## Lifecycle {#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 {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–9.6 | `pg_log` | — | pg_log |
| PG10–19 Beta 3 | `log` | — | log |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

log_directory sets the destination directory for log files. Can be specified as relative to the data directory or as absolute path. A relative path is resolved below the data directory, while an absolute path can place collector-managed files on a separate filesystem.

log_directory 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 {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Set log_directory as part of one end-to-end logging design. Validate collector behavior, rotation, ownership, shipping, retention, and recovery from a full destination. |
| OLAP | Size the log_directory path for bursty analytical output and verify that rotation or downstream ingestion cannot stall database processes. |
| Small nodes | Use a bounded, easily rotated log_directory configuration and monitor free space; a small node should not retain redundant formats or unlimited files. |
{.full-width}

## Pigsty {#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 | `/pg/log/postgres` | different | `{{ pg_log_dir }}` |
| OLAP | `/pg/log/postgres` | different | `{{ pg_log_dir }}` |
| CRIT | `/pg/log/postgres` | different | `{{ pg_log_dir }}` |
| TINY | `/pg/log/postgres` | different | `{{ pg_log_dir }}` |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = /pg/log/postgres (dcs); OLAP: PG9.0–19 Beta 3 = /pg/log/postgres (dcs); CRIT: PG9.0–19 Beta 3 = /pg/log/postgres (dcs); TINY: PG9.0–19 Beta 3 = /pg/log/postgres (dcs). Advice, pending human review — Editorial inference: A dedicated /pg/log/postgres path separates PostgreSQL logs from the data directory and matches the managed filesystem layout.

## Common pitfalls {#common-pitfalls}

- Editing log_directory 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.
- Changing log_directory globally without a rollback plan and a client or operational compatibility test.

## Related parameters {#related-parameters}

[`logging_collector`](/parameters/logging-collector/) · [`log_destination`](/parameters/log-destination/) · [`log_filename`](/parameters/log-filename/) · [`log_rotation_age`](/parameters/log-rotation-age/) · [`log_rotation_size`](/parameters/log-rotation-size/)

## References {#references}

- [PostgreSQL 19 Beta 3 — log_directory](https://www.postgresql.org/docs/19/runtime-config-logging.html#GUC-LOG-DIRECTORY)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)