Add db:get_by_index/2.

1 files changed, 14 insertions, 2 deletions

diff --git a/src/db.erl b/src/db.erl
index 8789757..50117e4 100644
--- a/src/db.erl
+++ b/src/db.erl
@@ -4,7 +4,7 @@
 %% API.
 -export([start_link/0, stop/0]).
 -export([init_db/0, init_db/1, init_tables/0, init_tables/1]).
--export([add/1, find/1]).
+-export([add/1, find/1, get_by_index/2]).
 %% API for testing.
 -export([dump/1, destroy_tables/0, info_tables/0, dump_to_file/1]).
 %% gen_server callbacks.
@@ -68,6 +68,9 @@ find(Hash) ->
 dump(Table) ->
     gen_server:call(?MODULE, {dump, Table}).
 
+get_by_index(Start, End) ->
+    gen_server:call(?MODULE, {get_by_index, {Start, End}}).
+
 %%%%%%%%%%%%%%%%%%%%
 handle_cast(_Request, State) ->
     {noreply, State}.
@@ -108,4 +111,13 @@ handle_call({find, Hash}, _From, State) ->
                  1 -> hd(Result);
                  _ -> duplicate_hash_in_db      % FIXME: log an error
              end,
-    {reply, Record, State}.
+    {reply, Record, State};
+handle_call({get_by_index, {Start, End}}, _From, State) ->
+    F = fun() ->
+                MatchHead = #plop{index = '$1', mtl = '$2', _ = '_'},
+                Guard = [{'>=', '$1', Start}, {'=<', '$1', End}],
+                Result = ['$2'],
+                mnesia:select(plop, [{MatchHead, Guard, Result}])
+        end,
+    Res = mnesia:transaction(F),
+    {reply, Res, State}.