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Diffstat (limited to 'nixos/modules/services/databases/postgresql.md')
-rw-r--r-- | nixos/modules/services/databases/postgresql.md | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/nixos/modules/services/databases/postgresql.md b/nixos/modules/services/databases/postgresql.md index 1805bafe3be38..4d66ee38be426 100644 --- a/nixos/modules/services/databases/postgresql.md +++ b/nixos/modules/services/databases/postgresql.md @@ -171,3 +171,40 @@ self: super: { }; } ``` + +## JIT (Just-In-Time compilation) {#module-services-postgres-jit} + +[JIT](https://www.postgresql.org/docs/current/jit-reason.html)-support in the PostgreSQL package +is disabled by default because of the ~300MiB closure-size increase from the LLVM dependency. It +can be optionally enabled in PostgreSQL with the following config option: + +```nix +{ + services.postgresql.enableJIT = true; +} +``` + +This makes sure that the [`jit`](https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-JIT)-setting +is set to `on` and a PostgreSQL package with JIT enabled is used. Further tweaking of the JIT compiler, e.g. setting a different +query cost threshold via [`jit_above_cost`](https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-JIT-ABOVE-COST) +can be done manually via [`services.postgresql.settings`](#opt-services.postgresql.settings). + +The attribute-names of JIT-enabled PostgreSQL packages are suffixed with `_jit`, i.e. for each `pkgs.postgresql` +(and `pkgs.postgresql_<major>`) in `nixpkgs` there's also a `pkgs.postgresql_jit` (and `pkgs.postgresql_<major>_jit`). +Alternatively, a JIT-enabled variant can be derived from a given `postgresql` package via `postgresql.withJIT`. +This is also useful if it's not clear which attribute from `nixpkgs` was originally used (e.g. when working with +[`config.services.postgresql.package`](#opt-services.postgresql.package) or if the package was modified via an +overlay) since all modifications are propagated to `withJIT`. I.e. + +```nix +with import <nixpkgs> { + overlays = [ + (self: super: { + postgresql = super.postgresql.overrideAttrs (_: { pname = "foobar"; }); + }) + ]; +}; +postgresql.withJIT.pname +``` + +evaluates to `"foobar"`. |