ignore_system_indexes

ignore_system_indexes — Disables reading from system indexes. Observed in PG9.0–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with backend context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Disables reading from system indexes.”

Identity

Type , Valuebool: Upstream pg_settings type
Context , Valuebackend: Fixed when a backend starts
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueDeveloper Options: 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

ignore_system_indexes makes a newly started backend read system catalogs without using their indexes, while catalog modifications still update the indexes. It is intended to recover from damaged system indexes.

Because its backend context is fixed at session start, changing the setting inside an existing session is ineffective. Catalog scans can become very slow.

The mode does not repair an index; it only creates a path to inspect data and REINDEX the damaged system index. Leaving it enabled hides symptoms and imposes broad catalog overhead. Its backend context fixes the value during connection startup; an existing session cannot change it.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Never use ignore_system_indexes as tuning or a steady-state availability setting. Stop writes, preserve immutable copies, exhaust backup/storage repair, document expected data loss, salvage narrowly, rebuild, and validate before any return to service.
OLAP	Read-only analytics does not make ignore_system_indexes safe: corrupted pages can still poison results or structures. Use only on a disposable salvage copy with explicit acceptance of lost data.
Small nodes	Do not enable ignore_system_indexes merely because no replica exists. Preserve the original first and seek a clean backup; this switch can convert visible corruption into silent loss.

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

Leaving ignore_system_indexes 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.

allow_system_table_mods · ignore_checksum_failure · zero_damaged_pages · shared_buffers