# enable_sort

> enable_sort — Enables the planner's use of explicit sort steps. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
---

> [!NOTE]
> **Fact — official short description:** “Enables the planner's use of explicit sort steps.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `bool` | Upstream pg_settings type |
| Context | `user` | Settable by an ordinary user |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Query Tuning / Planner Method Configuration | Upstream classification |
| Latest boot value | `on` | on |
{.fields meta="-"}

## Lifecycle {#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 {#default-history}

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

## How it works {#mechanism}

enable_sort controls whether the planner may choose explicit Sort nodes when no usable input order satisfies the requested pathkeys.

It is consulted while a plan is built. A session-level change is useful for comparing EXPLAIN alternatives, but an already cached plan is not retroactively rewritten; invalidation or replanning is required to observe a different choice.

Turning it off only discourages explicit sorting because correctness can still require a sort. Its user context permits session- or transaction-local changes; newly performed or newly planned work sees the value.

## Tuning advice {#tuning-advice}

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

| Workload | Guidance |
| --- | --- |
| OLTP | Keep the upstream default for routine OLTP. Use a transaction- or session-local change to diagnose whether choosing explicit Sort nodes when no usable input order satisfies the requested pathkeys explains a regression, then repair statistics, indexes, estimates, or query shape instead of leaving a cluster-wide method ban. |
| OLAP | Benchmark representative analytical plans with and without enable_sort. Judge planning time, memory, spill, and execution time together; a win for one report is not evidence for a global setting. |
| Small nodes | Do not use enable_sort as a permanent hint on a small host. Resource pressure may change the best method, so verify with EXPLAIN (ANALYZE, BUFFERS) and keep the change scoped to the affected workload if it is still needed. |
{.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: 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 {#common-pitfalls}

- Treating enable_sort as a query hint even though it affects every plan built in its scope.
- Testing an already cached prepared plan and concluding that the setting has no effect.
- Masking stale statistics or cardinality errors by disabling a plan method globally.
- Turning it off only discourages explicit sorting because correctness can still require a sort.

## Related parameters {#related-parameters}

[`work_mem`](/parameters/work-mem/) · [`temp_file_limit`](/parameters/temp-file-limit/) · [`enable_incremental_sort`](/parameters/enable-incremental-sort/) · [`enable_gathermerge`](/parameters/enable-gathermerge/) · [`trace_sort`](/parameters/trace-sort/)

## References {#references}

- [PostgreSQL 19 Beta 3 — enable_sort](https://www.postgresql.org/docs/19/runtime-config-query.html#GUC-ENABLE-SORT)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)