# output_plugin_libraries

> output_plugin_libraries lists libraries that may be named as logical decoding output plugins. It is a superuser setting present in PG14–18; the latest recorded boot default is pgoutput, test_decoding.
---

> [!NOTE]
> **Fact — official short description:** “Lists libraries that may be named as logical decoding output plugins.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `string` | Upstream pg_settings type |
| Context | `superuser` | Settable at runtime by a superuser |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Replication / Sending Servers | Upstream classification |
| Latest boot value | `pgoutput, test_decoding` | pgoutput, test_decoding |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG14 |
| Present in | PG14–19 Beta 3 |
| Removed in | No |
| Introduction commit | [`bf3842a64f5d`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=bf3842a64f5df489fab31b82aaeb9067ac938fde) — Add an output_plugin_libraries GUC to bless trusted output plugins |
| Commit date | 2026-08-10 |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG14–19 Beta 3 | `pgoutput, test_decoding` | — | pgoutput, test_decoding |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

Lists libraries that may be named as logical decoding output plugins. A superuser or a role granted SET privilege can change it for the relevant session or configuration scope.

Logical decoding accepts only output-plugin library names on this server-side allowlist, using LOAD-style naming with an exact plugin-name match. Adding a library is a trust decision because plugin code executes inside the server process.

Monitor and change output_plugin_libraries together with wal_level, max_wal_senders, max_replication_slots. Validate on the relevant server role and real workload, then use its superuser context to choose session change, reload, or restart; a historical boot default is not the current effective value.

## Tuning advice {#tuning-advice}

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

| Workload | Guidance |
| --- | --- |
| OLTP | List only installed, audited output plugins with a real consumer. Test with a least-privilege replication role and include plugin upgrades in the server release process. |
| OLAP | ETL decoding plugins are still in-process code; do not use broad paths for convenience. Test large-transaction memory, WAL retention, and plugin output. |
| Small nodes | Keep the small built-in allowlist without logical decoding. Before adding wal2json or another plugin, establish package provenance, version compatibility, and maintenance ownership. |
{.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 | `pgoutput, test_decoding, wal2json` | different | `'pgoutput, test_decoding, wal2json'` |
| OLAP | `pgoutput, test_decoding, wal2json` | different | `'pgoutput, test_decoding, wal2json'` |
| CRIT | `pgoutput, test_decoding, wal2json` | different | `'pgoutput, test_decoding, wal2json'` |
| TINY | `pgoutput, test_decoding, wal2json` | different | `'pgoutput, test_decoding, wal2json'` |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG14–19 Beta 3 = pgoutput, test_decoding, wal2json (dcs); OLAP: PG14–19 Beta 3 = pgoutput, test_decoding, wal2json (dcs); CRIT: PG14–19 Beta 3 = pgoutput, test_decoding, wal2json (dcs); TINY: PG14–19 Beta 3 = pgoutput, test_decoding, wal2json (dcs). Advice, pending human review — Editorial interpretation, pending human maintainer review: the override appears intended to make wal2json available while preserving a narrow explicit output-plugin allowlist; confirm it against the current Pigsty templates, hardware fixture, and operational guarantees before publication.

## Common pitfalls {#common-pitfalls}

- Changing it on the wrong primary, standby, sender, or subscriber role.
- Watching only configured bytes/time instead of actual lag, slot position, and worker state.
- Failing over to a node that lacks the old primary's capacity or prerequisites.
- Using infinite waits or WAL retention to hide a failed consumer.

## Related parameters {#related-parameters}

[`wal_level`](/parameters/wal-level/) · [`max_wal_senders`](/parameters/max-wal-senders/) · [`max_replication_slots`](/parameters/max-replication-slots/) · [`archive_mode`](/parameters/archive-mode/) · [`wal_log_hints`](/parameters/wal-log-hints/) · [`shared_preload_libraries`](/parameters/shared-preload-libraries/)

## References {#references}

- [PostgreSQL 19 Beta 3 — output_plugin_libraries](https://www.postgresql.org/docs/19/runtime-config-replication.html#GUC-OUTPUT-PLUGIN-LIBRARIES)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)