From e7a1ca43af470b6e99c0e11d845903f9bf00c723 Mon Sep 17 00:00:00 2001
From: Linus Nordberg <linus@nordberg.se>
Date: Tue, 9 Sep 2014 14:04:19 +0200
Subject: Add db:get_by_index_sorted/2.

---
 src/db.erl | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/src/db.erl b/src/db.erl
index f683d48..aa6cc29 100644
--- a/src/db.erl
+++ b/src/db.erl
@@ -7,7 +7,7 @@
 %% 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, get_by_index/2, size/0]).
+-export([add/1, find/1, get_by_index/2, get_by_index_sorted/2, size/0]).
 %% API for testing.
 -export([dump/1, destroy_tables/0, info_tables/0, dump_to_file/1]).
 %% gen_server callbacks.
@@ -68,7 +68,9 @@ start_link() ->
 stop() ->
     gen_server:call(?MODULE, stop).
 
-%% API.
+%%%%%%%%%%%%%%%%%%%%
+%% Public API.
+
 add(Entry) ->
     gen_server:call(?MODULE, {add, Entry}).
 
@@ -81,7 +83,13 @@ dump(Table) ->
 get_by_index(Start, End) ->
     gen_server:call(?MODULE, {get_by_index, {Start, End}}).
 
+get_by_index_sorted(Start, End) ->
+    gen_server:call(?MODULE, {get_by_index_sorted, {Start, End}}).
+
+
 %%%%%%%%%%%%%%%%%%%%
+%% gen_server callbacks.
+
 handle_cast(_Request, State) ->
     {noreply, State}.
 
@@ -95,7 +103,10 @@ terminate(_Reason, _State) ->
     io:format("~p terminating~n", [?MODULE]),
     ok.
 
+
 %%%%%%%%%%%%%%%%%%%%
+%% The meat.
+
 handle_call(stop, _From, State) ->
     {stop, normal, stopped, State};
 handle_call({add, Entry}, _From, State) ->
@@ -123,11 +134,22 @@ handle_call({find, Hash}, _From, State) ->
              end,
     {reply, Record, State};
 handle_call({get_by_index, {Start, End}}, _From, State) ->
+    Res = [X || [_, X] <- select_index(Start, End)],
+    {reply, Res, State};
+handle_call({get_by_index_sorted, {Start, End}}, _From, State) ->
+    %% FIXME: RAM hog -- how bad is it?
+    Res = [X || [_, X] <- lists:sort(select_index(Start, End))],
+    {reply, Res, State}.
+
+%%%%%%%%%%%%%%%%%%%%
+%% Helper functions.
+
+select_index(Start, End) ->
     F = fun() ->
                 MatchHead = #plop{index = '$1', mtl = '$2', _ = '_'},
                 Guard = [{'>=', '$1', Start}, {'=<', '$1', End}],
-                Result = ['$2'],
+                Result = ['$$'],
                 mnesia:select(plop, [{MatchHead, Guard, Result}])
         end,
     {atomic, Res} = mnesia:transaction(F),
-    {reply, Res, State}.
+    Res.
-- 
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