nixos/modules/server/postgresql.nix

{ config, lib, pkgs, ... }:
with lib;
let cfg = config.void.server.postgresql;
in {
  options.void.server.postgresql = { enable = mkEnableOption false; };

  config = mkIf cfg.enable {
    services.postgresql = {
      enable = true;
      package = pkgs.postgresql_17_jit;
      ensureDatabases = [ "forgejo" "akkoma" "nextcloud" ];
      ensureUsers = [
        {
          name = "postgres";
          ensureClauses = {
            superuser = true;
            login = true;
            createrole = true;
            createdb = true;
            replication = true;
          };
        }
        {
          name = "forgejo";
          ensureDBOwnership = true;
        }
        {
          name = "akkoma";
          ensureDBOwnership = true;
        }
        {
          name = "nextcloud";
          ensureDBOwnership = true;
        }
      ];
      # Thank you NotAShelf
      # https://github.com/NotAShelf/nyx/blob/d407b4d6e5ab7f60350af61a3d73a62a5e9ac660/modules/core/roles/server/system/services/databases/postgresql.nix#L74
      settings = {
        # Connectivity;
        max_connections = 100;
        superuser_reserved_connections = 3;

        # Memory Settings;
        shared_buffers = "1024 MB";
        work_mem = "32 MB";
        maintenance_work_mem = "320 MB";
        huge_pages = "off";
        effective_cache_size = "2 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,auto_explain"; # per statement resource usage stats & log explain statements for slow queries
        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";

        jit_above_cost = 100000;
        jit_inline_above_cost = 150000;
        jit_optimize_above_cost = 500000;

        # log slow queries
        log_min_duration_statement = 100;
        "auto_explain.log_min_duration" = 100;

        # logging configuration
        log_connections = true;
        log_statement = "all";
        logging_collector = true;
        log_disconnections = true;
        log_destination = lib.mkForce "syslog";
      };
    };
  };
}