diff --git a/src/mnesia_rocksdb_admin.erl b/src/mnesia_rocksdb_admin.erl
index 3ae2c22..73953e3 100644
--- a/src/mnesia_rocksdb_admin.erl
+++ b/src/mnesia_rocksdb_admin.erl
@@ -1489,11 +1489,7 @@ open_db_(MP, Alias, Opts, CFs0, CreateIfMissing) ->
             %% not yet created
             CFs = cfs(CFs0),
             file:make_dir(MP),
-            OpenOpts = [ {create_if_missing, true}
-                       , {create_missing_column_families, true}
-                       , {merge_operator, erlang_merge_operator}
-                       | Opts ],
-            OpenRes = mnesia_rocksdb_lib:open_rocksdb(MP, OpenOpts, CFs),
+            OpenRes = rocksdb_open(MP, Opts, CFs),
             map_cfs(OpenRes, CFs, Alias, Acc0);
         false ->
             {error, enoent};
@@ -1504,9 +1500,15 @@ open_db_(MP, Alias, Opts, CFs0, CreateIfMissing) ->
             map_cfs(rocksdb_open(MP, Opts, CFs1), CFs1, Alias, Acc0)
     end.
 
+open_opts(Opts) ->
+    [ {create_if_missing, true}
+    , {create_missing_column_families, true}
+    , {merge_operator, erlang_merge_operator}
+    | Opts ].
+
 rocksdb_open(MP, Opts, CFs) ->
     %% rocksdb:open(MP, Opts, CFs),
-    mnesia_rocksdb_lib:open_rocksdb(MP, Opts, CFs).
+    mnesia_rocksdb_lib:open_rocksdb(MP, open_opts(Opts), CFs).
 
 is_open(Alias, #st{backends = Bs}) ->
     case maps:find(Alias, Bs) of
diff --git a/src/mrdb.erl b/src/mrdb.erl
index 9be0a4a..74025a0 100644
--- a/src/mrdb.erl
+++ b/src/mrdb.erl
@@ -53,6 +53,7 @@
         , delete/2       , delete/3
         , delete_object/2, delete_object/3
         , match_delete/2
+        , merge/3        , merge/4
 	, clear_table/1
         , batch_write/2  , batch_write/3
         , update_counter/3, update_counter/4
@@ -740,6 +741,21 @@ insert(Tab, Obj0, Opts) ->
     EncVal = encode_val(Obj, Ref),
     insert_(Ref, Key, encode_key(Key, Ref), EncVal, Obj, Opts).
 
+merge(Tab, Key, MergeOp) ->
+    merge(Tab, Key, MergeOp, []).
+
+merge(Tab, Key, MergeOp, Opts) ->
+    #{encoding := Enc} = Ref = ensure_ref(Tab),
+    case Enc of
+        {_, {value, term}} ->
+            merge_(Ref, Key, MergeOp, Opts);
+        _ ->
+            abort(badarg)
+    end.
+
+merge_(Ref, Key, MergeOp, Opts) ->
+    rdb_merge(Ref, encode_key(Key), MergeOp, Opts).
+
 validate_obj(Obj, #{mode := mnesia}) ->
     Obj;
 validate_obj(Obj, #{attr_pos := AP,