small update

modules/services/postgresql.mod.nix

@@ -0,0 +1,124 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: let
+  inherit (lib.modules) mkIf;
+  inherit (lib.options) mkEnableOption;
+
+  cfg = config.modules.system.services.database.postgresql;
+in {
+  options.modules.system.services.database.postgresql.enable = mkEnableOption "postgresql";
+
+  config = mkIf cfg.enable {
+    services.postgresql = {
+      enable = true;
+      package = pkgs.postgresql_17;
+      # NOTE: it is imperative to create this manually when starting postgresql.
+      dataDir = "/srv/data/postgresql/${config.services.postgresql.package.psqlSchema}";
+
+      # Whether PostgreSQL should listen on all network interfaces.
+      # If disabled, the database can only be accessed via its Unix domain socket or via TCP connections to localhost.
+      enableTCPIP = false;
+
+      # Check the syntax of the configuration file at compile time
+      checkConfig = true;
+
+      ensureDatabases = [
+        "git"
+        "grafana"
+        "stalwart"
+        "plausible"
+      ];
+
+      ensureUsers = [
+        {
+          name = "postgres";
+          ensureClauses = {
+            superuser = true;
+            login = true;
+            createrole = true;
+            createdb = true;
+            replication = true;
+          };
+        }
+        {
+          name = "git";
+          ensureDBOwnership = true;
+        }
+        {
+          name = "grafana";
+          ensureDBOwnership = true;
+        }
+        {
+          name = "stalwart";
+          ensureDBOwnership = true;
+        }
+        {
+          name = "plausible";
+          ensureDBOwnership = true;
+        }
+      ];
+      settings = {
+        # taken from https://pgconfigurator.cybertec.at/
+
+        # Connectivity
+        max_connections = 100;
+        superuser_reserved_connections = 3;
+
+        # Memory Settings
+        shared_buffers = "2048 MB";
+        work_mem = "32 MB";
+        maintenance_work_mem = "320 MB";
+        huge_pages = "off";
+        effective_cache_size = "6 GB";
+        effective_io_concurrency = 100; # concurrent IO only really activated if OS supports posix_fadvise function
+        random_page_cost = 1.25; # speed of random disk access relative to sequential access (1.0)
+
+        # Monitoring
+        shared_preload_libraries = "pg_stat_statements"; # per statement resource usage stats;
+        track_io_timing = "on"; # measure exact block IO times;
+        track_functions = "pl"; # track execution times of pl-language procedures if any;
+
+        # Replication
+        wal_level = "replica"; # consider using at least 'replica';
+        max_wal_senders = 0;
+        synchronous_commit = "on";
+
+        # Checkpointing: ;
+        checkpoint_timeout = "15 min";
+        checkpoint_completion_target = 0.9;
+        max_wal_size = "1024 MB";
+        min_wal_size = "512 MB";
+        # WAL writing
+        wal_compression = "on";
+        wal_buffers = -1; # auto-tuned by Postgres till maximum of segment size (16MB by default);
+        wal_writer_delay = "200ms";
+        wal_writer_flush_after = "1MB";
+
+        # Background writer;
+        bgwriter_delay = "200ms";
+        bgwriter_lru_maxpages = 100;
+        bgwriter_lru_multiplier = 2.0;
+        bgwriter_flush_after = 0;
+
+        # Parallel queries: ;
+        max_worker_processes = 6;
+        max_parallel_workers_per_gather = 3;
+        max_parallel_maintenance_workers = 3;
+        max_parallel_workers = 6;
+        parallel_leader_participation = "on";
+
+        # Advanced features ;
+        enable_partitionwise_join = "on";
+        enable_partitionwise_aggregate = "on";
+        jit = "on";
+        max_slot_wal_keep_size = "1000 MB";
+        track_wal_io_timing = "on";
+        maintenance_io_concurrency = 100;
+        wal_recycle = "on";
+      };
+    };
+  };
+}