debug_print_rewritten

debug_print_rewritten is the PostgreSQL setting that controls whether PostgreSQL logs each query’s rewritten parse tree.

Note

Fact — official short description: “Logs each query’s rewritten parse tree.”

Identity

Type , Valuebool: Upstream pg_settings type
Context , Valueuser: Settable by an ordinary user
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueReporting and Logging / What to Log: Upstream classification
Latest boot value , Valueoff: off

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

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.0–19 Beta 3	`off`	—	off

How it works

debug_print_rewritten logs each query’s rewritten parse tree. It exposes the query tree after rule rewriting, which is useful for diagnosing views and rules but can generate very large logs.

debug_print_rewritten is a USER-context setting. An authorized role can change it for a session, while ALTER ROLE or ALTER DATABASE can establish a default for future sessions.

The debug_print_* switches feed the normal server logging path, so log_min_messages, log_destination, and collector capacity determine whether the output is retained safely.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Do not tune or enable debug_print_rewritten globally in production. If server-developer diagnostics require it, isolate one session, bound its duration, and route the resulting logs safely.
OLAP	Do not use debug_print_rewritten as a substitute for EXPLAIN on analytical SQL; capture a targeted plan instead of dumping every internal tree.
Small nodes	Leave debug_print_rewritten at its normal default. Verbose internal trees can exhaust a small node’s log I/O and disk unexpectedly.

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	—	—

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Changing debug_print_rewritten in one session and assuming role defaults, database defaults, or other pooled sessions changed with it.
Leaving an internal-tree dump enabled globally and overwhelming log I/O, storage, or ingestion.
Treating debug output as a stable public format or as a substitute for targeted EXPLAIN diagnostics.
Changing debug_print_rewritten globally without a rollback plan and a client or operational compatibility test.

debug_pretty_print · debug_print_parse · debug_print_plan · log_min_messages · client_min_messages