Share cursors managed stored in the module's ets table.

src/riak_kv_wterl_backend.erl

@@ -52,6 +52,7 @@
 
 -record(state, {table :: string(),
                 connection :: wterl:connection(),
+		cursors :: ets:tid(),
                 session :: wterl:session()}).
 
 -type state() :: #state{}.
@@ -100,10 +101,16 @@ start(Partition, Config) ->
 
 %% @doc Stop the wterl backend
 -spec stop(state()) -> ok.
-stop(#state{session=undefined}) ->
+stop(#state{session=undefined, cursors=undefined}) ->
     ok;
-stop(#state{session=Session}) ->
+stop(#state{session=Session, cursors=undefined}) ->
-    ok = wterl:session_close(Session).
+    ok = wterl:session_close(Session);
+stop(#state{session=Session, cursors=Cursors}=State) ->
+    ets:foldl(fun({_Table, Cursor}, _) ->
+		      ok = wterl:cursor_close(Cursor)
+              end, true, Cursors),
+    ets:delete(Cursors),
+    stop(State#state{session=Session, cursors=undefined}).
 
 %% @doc Retrieve an object from the wterl backend
 -spec get(riak_object:bucket(), riak_object:key(), state()) ->
@@ -112,9 +119,10 @@ stop(#state{session=Session}) ->
                  {error, term(), state()}.
 get(Bucket, Key, #state{session=undefined}=State) ->
     get(Bucket, Key, establish_session(State));
-get(Bucket, Key, #state{session=Session, table=Table}=State) ->
+get(Bucket, Key, #state{session=Session, table=Table}=State0) ->
     WTKey = to_object_key(Bucket, Key),
-    case wterl:session_get(Session, Table, WTKey) of
+    {Cursor, State} = cursor(Session, Table, get, State0),
+    case wterl:cursor_search(Cursor, WTKey) of
         {ok, Value} ->
             {ok, Value, State};
         not_found  ->
@@ -133,9 +141,10 @@ get(Bucket, Key, #state{session=Session, table=Table}=State) ->
                  {error, term(), state()}.
 put(Bucket, PrimaryKey, IndexSpecs, Val, #state{session=undefined}=State) ->
     put(Bucket, PrimaryKey, IndexSpecs, Val, establish_session(State));
-put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{session=Session, table=Table}=State) ->
+put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{session=Session, table=Table}=State0) ->
     WTKey = to_object_key(Bucket, PrimaryKey),
-    case wterl:session_put(Session, Table, WTKey, Val) of
+    {Cursor, State} = cursor(Session, Table, put, State0),
+    case wterl:cursor_insert(Cursor, WTKey, Val) of
         ok ->
             {ok, State};
         {error, Reason} ->
@@ -151,9 +160,10 @@ put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{session=Session, table=Table}=S
                     {error, term(), state()}.
 delete(Bucket, Key, IndexSpecs, #state{session=undefined}=State) ->
     delete(Bucket, Key, IndexSpecs, establish_session(State));
-delete(Bucket, Key, _IndexSpecs, #state{session=Session, table=Table}=State) ->
+delete(Bucket, Key, _IndexSpecs, #state{session=Session, table=Table}=State0) ->
     WTKey = to_object_key(Bucket, Key),
-    case wterl:session_delete(Session, Table, WTKey) of
+    {Cursor, State} = cursor(Session, Table, delete, State0),
+    case wterl:cursor_remove(Cursor, WTKey) of
         ok ->
             {ok, State};
         {error, Reason} ->
@@ -324,6 +334,19 @@ callback(_Ref, _Msg, State) ->
 %% Internal functions
 %% ===================================================================
 
+cursor(Session, Table, Type, #state{cursors=undefined}=State) ->
+    Cursors = ets:new(?MODULE, [{read_concurrency, true}]),
+    cursor(Session, Table, Type, State#state{cursors=Cursors});
+cursor(Session, Table, Type, #state{cursors=Cursors}=State) ->
+    case ets:lookup(Cursors, {Type, Table}) of
+	[{{_Type, Table}, Cursor}] ->
+	    {Cursor, State};
+	_ ->
+	    {ok, Cursor} = wterl:cursor_open(Session, Table),
+	    ets:insert(Cursors, {Table, Cursor}),
+	    {Cursor, State}
+    end.
+
 %% @private
 establish_connection(Table, Config) ->
     %% Get the data root directory