From 482619dac70c36b0876223d95daf5a8ef616c0fb Mon Sep 17 00:00:00 2001
From: Matthieu Coudron <886074+teto@users.noreply.github.com>
Date: Thu, 17 Aug 2023 19:19:54 +0200
Subject: [PATCH 1/3] services.postgres: move the generated statement at the
 top of the file

---
 nixos/modules/services/databases/postgresql.nix | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/nixos/modules/services/databases/postgresql.nix b/nixos/modules/services/databases/postgresql.nix
index 0acaf0fd00a6..50d0709bcd8f 100644
--- a/nixos/modules/services/databases/postgresql.nix
+++ b/nixos/modules/services/databases/postgresql.nix
@@ -464,13 +464,16 @@ in
 
     services.postgresql.dataDir = mkDefault "/var/lib/postgresql/${cfg.package.psqlSchema}";
 
-    services.postgresql.authentication = mkAfter
+    services.postgresql.authentication = mkMerge [
+      (mkBefore "# Generated file; do not edit!")
+      (mkAfter
       ''
-        # Generated file; do not edit!
+        # default value of services.postgresql.authentication
         local all all              peer
         host  all all 127.0.0.1/32 md5
         host  all all ::1/128      md5
-      '';
+      '')
+    ];
 
     users.users.postgres =
       { name = "postgres";

From 956a1876aa635227807bc7c620e46933a06a5ef6 Mon Sep 17 00:00:00 2001
From: Matthieu Coudron <886074+teto@users.noreply.github.com>
Date: Thu, 17 Aug 2023 19:21:16 +0200
Subject: [PATCH 2/3] services.postgresql: add identMap example

to make things clearer
---
 nixos/modules/services/databases/postgresql.nix | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/nixos/modules/services/databases/postgresql.nix b/nixos/modules/services/databases/postgresql.nix
index 50d0709bcd8f..9e12227fc753 100644
--- a/nixos/modules/services/databases/postgresql.nix
+++ b/nixos/modules/services/databases/postgresql.nix
@@ -106,12 +106,14 @@ in
       identMap = mkOption {
         type = types.lines;
         default = "";
+        example = literalExample ''
+          map-name-0 system-username-0 database-username-0
+          map-name-1 system-username-1 database-username-1
+        '';
         description = lib.mdDoc ''
           Defines the mapping from system users to database users.
 
-          The general form is:
-
-          map-name system-username database-username
+          See the [auth doc](https://postgresql.org/docs/current/auth-username-maps.html).
         '';
       };
 

From b53c715e504fa1a2a3c2f252a0d714170b03f92d Mon Sep 17 00:00:00 2001
From: Matthieu Coudron <886074+teto@users.noreply.github.com>
Date: Thu, 17 Aug 2023 20:18:45 +0200
Subject: [PATCH 3/3] services.postgres: add initialScript example

---
 nixos/modules/services/databases/postgresql.nix | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/nixos/modules/services/databases/postgresql.nix b/nixos/modules/services/databases/postgresql.nix
index 9e12227fc753..7b30360590ec 100644
--- a/nixos/modules/services/databases/postgresql.nix
+++ b/nixos/modules/services/databases/postgresql.nix
@@ -130,6 +130,11 @@ in
       initialScript = mkOption {
         type = types.nullOr types.path;
         default = null;
+        example = literalExpression ''
+          pkgs.writeText "init-sql-script" '''
+            alter user postgres with password 'myPassword';
+          ''';'';
+
         description = lib.mdDoc ''
           A file containing SQL statements to execute on first startup.
         '';