update update-postgres script

nixos/roles/update-postgres.nix

@@ -3,26 +3,32 @@
   pkgs,
   ...
 }: {
-  containers.temp-pg.config.services.postgresql = {
-    enable = true;
-    package = pkgs.postgresql_14;
-  };
   environment.systemPackages = let
-    newpg = config.containers.temp-pg.config.services.postgresql;
+    # script from:
+    # https://nixos.org/manual/nixos/stable/index.html#module-postgresql
+    # 1) bump toVersion; rebuild
+    # 2) run this script
+    # 3) bump postgres; rebuild
+    # 4) run analyze_new_cluster.sh; delete_old_cluster.sh from the database dir.
+    toVersion = "14"; # Bump this when there is a new version.
+    new_package = "postgres_${toVersion}";
   in [
     (pkgs.writeScriptBin "upgrade-pg-cluster" ''
-      set -x
+      set -eux
+
+      systemctl stop postgresql
+
+      export NEWDATA="/var/lib/postgresql/${toVersion}"
+
+      export NEWBIN="${pkgs.${new_package}}/bin"
+
       export OLDDATA="${config.services.postgresql.dataDir}"
-      export NEWDATA="${newpg.dataDir}"
       export OLDBIN="${config.services.postgresql.package}/bin"
-      export NEWBIN="${newpg.package}/bin"
 
       install -d -m 0700 -o postgres -g postgres "$NEWDATA"
       cd "$NEWDATA"
       sudo -u postgres $NEWBIN/initdb -D "$NEWDATA"
 
-      systemctl stop postgresql    # old one
-
       sudo -u postgres $NEWBIN/pg_upgrade \
         --old-datadir "$OLDDATA" --new-datadir "$NEWDATA" \
         --old-bindir $OLDBIN --new-bindir $NEWBIN \