# backtrace_functions

> backtrace_functions — Log backtrace for errors in these functions. Observed in PG13–19 Beta 3; its last measured boot default is empty string in PG19 Beta 3, with superuser context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
---

> [!NOTE]
> **Fact — official short description:** “Log backtrace for errors in these functions.”

## 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 | Developer Options | Upstream classification |
| Latest boot value | `""` | empty string |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG13 |
| Present in | PG13–19 Beta 3 |
| Removed in | No |
| Introduction commit | [`71a8a4f6e365`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=71a8a4f6e36547bb060dbcc961ea9b57420f7190) — Add backtrace support for error reporting |
| Commit date | 2019-11-08 |
| Discussion | [thread 1](https://postgr.es/m//5f48cb47-bf1e-05b6-7aae-3bf2cd01586d@2ndquadrant.com) · [thread 2](https://postgr.es/m/CAMsr+YGL+yfWE=JvbUbnpWtrRZNey7hJ07+zT4bYJdVp4Szdrg@mail.gmail.com) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG13–19 Beta 3 | `""` | — | empty string |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

backtrace_functions is a comma-separated list of internal C function names. If an error originates in a listed function, PostgreSQL appends a native backtrace to that error in the server log.

It matches C symbols, not SQL function names. Availability and symbol quality depend on platform, compiler, build flags, debug information, and whether functions were inlined.

The setting can target a narrow failure path without logging stacks for every error. Stack traces can expose implementation detail and increase log volume, so collection should be scoped and protected. Its superuser context permits an authorized session change without a server restart.

## Tuning advice {#tuning-advice}

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

| Workload | Guidance |
| --- | --- |
| OLTP | Do not tune production OLTP with backtrace_functions. Enable it only for a bounded reproduction with an owner, log/disk budget, rollback condition, and evidence-capture plan; restore the default immediately afterward. |
| OLAP | Long analytical runs can amplify backtrace_functions's debug overhead and artifacts. Prefer standard EXPLAIN and statistics first, and isolate any developer experiment from normal users. |
| Small nodes | Keep backtrace_functions at its upstream default. A small host has less spare CPU, disk, connection, and log capacity for developer instrumentation. |
{.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 | Unmodified | — | — |
| OLAP | Unmodified | — | — |
| CRIT | Unmodified | — | — |
| TINY | Unmodified | — | — |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG13–19 Beta 3 unmodified; OLAP: PG13–19 Beta 3 unmodified; CRIT: PG13–19 Beta 3 unmodified; TINY: PG13–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Leaving backtrace_functions enabled after the bounded diagnostic or recovery task.
- Running the experiment on the only copy of production data.
- Underestimating log, core-file, temporary-file, WAL, CPU, or connection-slot amplification.
- Treating a server that merely starts or completes a query as proof that data and behavior are correct.

## Related parameters {#related-parameters}

[`log_error_verbosity`](/parameters/log-error-verbosity/) · [`log_min_error_statement`](/parameters/log-min-error-statement/) · [`compute_query_id`](/parameters/compute-query-id/) · [`log_line_prefix`](/parameters/log-line-prefix/)

## References {#references}

- [PostgreSQL 19 Beta 3 — backtrace_functions](https://www.postgresql.org/docs/19/runtime-config-developer.html#GUC-BACKTRACE-FUNCTIONS)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)