key with test.

mnesia/ggs_db.erl

@@ -7,7 +7,7 @@
 -module(ggs_db).
 -import(mnesia).
 %-compile({no_auto_import,[length/2]}).
--export([init/0,setItem/4,getItem/3,removeItem/3,length/2]).
+-export([init/0,setItem/4,getItem/3,removeItem/3,key/3,length/2]).
 -include("ggs_db.hrl").
 
 %%-----------------------------------------------------
@@ -63,4 +63,11 @@ length(Db,Ns) ->
     {atomic, Ret} = mnesia:transaction(Fun),
     Ret.
 
-
+key(Db,Ns,Position) ->
+    Fun = fun() ->
+                Keys = mnesia:all_keys(data),
+                Rest = lists:filter(fun({A,B,_}) -> ((A==Db) and (B==Ns)) end, Keys),
+                lists:nth(Position, Rest)
+          end,
+    {atomic, Ret} = mnesia:transaction(Fun),
+    Ret.

mnesia/ggs_db_test.erl

@@ -24,9 +24,12 @@ length_test() ->
 
 removeItem_test() ->
     ggs_db:removeItem(1,1,4),
-    ?assertNot(ggs_db:getItem(1,1,4) =:= {atomic,"114"}),
-    mnesia:stop().
+    ?assertNot(ggs_db:getItem(1,1,4) =:= {atomic,"114"}).
+    %mnesia:stop().
 
+key_test() ->
+    ?assert(ggs_db:key(1,1,2) =:= {1,1,3}),
+    mnesia:stop().
 %cleanup(Val) ->
 %    mnesia:stop().