fix restore if database does not exists

checks/postgresql/default.nix

@@ -63,5 +63,10 @@
       output = machine.succeed("runuser -u postgres -- /run/current-system/sw/bin/psql --csv -c \"SELECT datdba::regrole FROM pg_database WHERE datname = 'test'\"")
       owner = output.split("\n")[1]
       assert owner == "test", f"Expected database owner to be 'test', got '{owner}'"
+
+      # check if restore works if the database does not exist
+      machine.succeed("runuser -u postgres -- dropdb test")
+      machine.succeed("${nodes.machine.clanCore.state.postgresql-test.postRestoreCommand}")
+      machine.succeed("runuser -u postgres -- /run/current-system/sw/bin/psql -d test -c '\dt' >&2")
     '';
 })

clanModules/postgresql/default.nix

@@ -146,6 +146,7 @@ in
             pkgs.coreutils
             pkgs.util-linux
             pkgs.zstd
+            pkgs.gnugrep
           ]
         }
         while [[ "$(systemctl is-active postgresql)" == activating ]]; do
@@ -167,7 +168,9 @@ in
             }
 
             mkdir -p "${folder}"
-            runuser -u postgres -- dropdb "${db.name}"
+            if runuser -u postgres -- psql -d postgres -c "SELECT 1 FROM pg_database WHERE datname = '${db.name}'" | grep -q 1; then
+              runuser -u postgres -- dropdb "${db.name}"
+            fi
             runuser -u postgres -- pg_restore -C -d postgres "${current}"
           )
         else