# jit_debugging_support

> jit_debugging_support — Register JIT-compiled functions with debugger. Observed in PG11–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with superuser-backend context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
---

> [!NOTE]
> **Fact — official short description:** “Register JIT-compiled functions with debugger.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `bool` | Upstream pg_settings type |
| Context | `superuser-backend` | Fixed when a superuser backend starts |
| 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 | `off` | off |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG11 |
| Present in | PG11–19 Beta 3 |
| Removed in | No |
| Introduction commit | [`250bca7fc145`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=250bca7fc145b143d5e9aeeca66f0bb36cf4d5ef) — Debugging and profiling support for LLVM JIT provider. |
| Commit date | 2018-03-22 |
| Discussion | [thread 1](https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG11–19 Beta 3 | `off` | — | off |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

jit_debugging_support registers generated JIT functions with GDB when LLVM and the platform provide the required listener interfaces. It improves symbol visibility for debugger sessions.

The value is fixed at backend start and does not enable JIT itself. Queries still need jit, a provider, and cost thresholds to generate code.

Registration adds developer instrumentation and is useful only while debugging JIT internals or generated code. It is not a query-performance feature. Its superuser-backend context fixes the value during connection startup and restricts who may set it.

## 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 jit_debugging_support. 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 jit_debugging_support's debug overhead and artifacts. Prefer standard EXPLAIN and statistics first, and isolate any developer experiment from normal users. |
| Small nodes | Keep jit_debugging_support 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: PG11–19 Beta 3 unmodified; OLAP: PG11–19 Beta 3 unmodified; CRIT: PG11–19 Beta 3 unmodified; TINY: PG11–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Leaving jit_debugging_support 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}

[`jit`](/parameters/jit/) · [`jit_above_cost`](/parameters/jit-above-cost/) · [`jit_dump_bitcode`](/parameters/jit-dump-bitcode/) · [`jit_profiling_support`](/parameters/jit-profiling-support/) · [`jit_expressions`](/parameters/jit-expressions/)

## References {#references}

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