jit_debugging_support

Definition PG 18 manual

If LLVM has the required functionality, register generated functions with GDB. This makes debugging easier. The default setting is off. Only superusers and users with the appropriate SET privilege can change this parameter at session start, and it cannot be changed at all within a session.

How it works

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.

Operational considerations

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.

Workload guidance

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.

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.

SMALL: Keep jit_debugging_support at its upstream default. A small host has less spare CPU, disk, connection, and log capacity for developer instrumentation.