[#314] Adding count_by function

src/adapter_test_helpers/sumo_basic_test_helper.erl

@@ -10,6 +10,7 @@
   delete/1,
   check_proper_dates/1,
   count/1,
+  count_by/1,
   persist_using_changeset/1
 ]).
 
@@ -194,6 +195,18 @@ count(Config) ->
   6 = sumo:count(Name),
   ok.
 
+-spec count_by(config()) -> ok.
+count_by(Config) ->
+  {_, Name} = lists:keyfind(name, 1, Config),
+
+  6 = sumo:count_by(Name, [{age, '>', 2}]),
+  4 = sumo:count_by(Name, [{age, '>', 2}, {age, '=<', 5}]),
+  2 = sumo:count_by(Name, [{age, '>', 5}]),
+  0 = sumo:count_by(Name, [{age, '>', 7}]),
+  8 = sumo:count_by(Name, []),
+
+  ok.
+
 -spec persist_using_changeset(config()) -> ok.
 persist_using_changeset(Config) ->
   {_, Name} = lists:keyfind(name, 1, Config),

src/adapter_test_helpers/sumo_find_test_helper.erl

@@ -64,4 +64,4 @@ init_store(Name) ->
   sumo:persist(Name, Module:new(<<"D">>, <<"B">>, 4)),
   sumo:persist(Name, Module:new(<<"E">>, <<"A">>, 2)),
   sumo:persist(Name, Module:new(<<"F">>, <<"E">>, 1)),
-  ok.
+  ok.

src/adapters/sumo_store_mnesia.erl

@@ -33,7 +33,8 @@
   delete_all/2,
   find_all/2, find_all/5,
   find_by/3, find_by/5, find_by/6,
-  count/2
+  count/2,
+  count_by/3
 ]).
 
 %%%=============================================================================
@@ -245,6 +246,21 @@ count(DocName, State) ->
     _:Reason -> {error, Reason, State}
   end.
 
+-spec count_by(DocName, Conditions, State) -> Response when
+  DocName    :: sumo:schema_name(),
+  Conditions :: sumo:conditions(),
+  State      :: state(),
+  Response   :: sumo_store:result(non_neg_integer(), state()).
+count_by(DocName, Conditions, State) ->
+  MatchSpec = build_match_spec(DocName, Conditions),
+  Transaction = fun() ->
+    length(mnesia:select(DocName, MatchSpec))
+  end,
+  case mnesia:transaction(Transaction) of
+    {aborted, Reason} -> {error, Reason, State};
+    {atomic, Count}   -> {ok, Count, State}
+  end.
+
 %%%=============================================================================
 %%% Internal functions
 %%%=============================================================================

src/sumo.erl

@@ -46,6 +46,7 @@
   delete_by/2,
   delete_all/1,
   count/1,
+  count_by/2,
   call/2, call/3
 ]).
 
@@ -270,6 +271,14 @@ count(DocName) ->
     Error       -> exit(Error)
   end.
 
+%% @doc Counts the total number of docs matching the provided Conditions.
+-spec count_by(schema_name(), conditions()) -> non_neg_integer().
+count_by(DocName, Conditions) ->
+  case sumo_store:count_by(sumo_config:get_store(DocName), DocName, Conditions) of
+    {ok, Total} -> Total;
+    Error       -> exit(Error)
+  end.
+
 %% @doc Calls the given custom function of a store.
 -spec call(schema_name(), atom()) -> term().
 call(DocName, Function) ->

src/sumo_store.erl

@@ -37,6 +37,7 @@
   find_by/5,
   find_by/6,
   count/2,
+  count_by/3,
   call/4
 ]).
 
@@ -130,6 +131,11 @@
   Schema :: sumo:schema_name(),
   Res    :: result(non_neg_integer(), State).
 
+-callback count_by(Schema, Conditions, State) -> Res when
+  Schema     :: sumo:schema_name(),
+  Conditions :: sumo:conditions(),
+  Res        :: result(non_neg_integer(), State).
+
 %%%=============================================================================
 %%% API
 %%%=============================================================================
@@ -257,6 +263,15 @@ find_by(Name, DocName, Conditions, SortFields, Limit, Offset) ->
 count(Name, DocName) ->
   wpool:call(Name, {count, DocName}).
 
+%% @doc Counts the total number of docs that match the given conditions.
+-spec count_by(Name, DocName, Conditions) -> Res when
+  Name       :: atom(),
+  DocName    :: sumo:schema_name(),
+  Conditions :: sumo:conditions(),
+  Res        :: {ok, non_neg_integer()} | {error, term()}.
+count_by(Name, DocName, Conditions) ->
+  wpool:call(Name, {count_by, DocName, Conditions}).
+
 %% @doc Calls a custom function in the given store name.
 -spec call(Name, DocName, Function, Args) -> Res when
   Name     :: atom(),
@@ -372,6 +387,13 @@ handle_call(
   {OkOrError, Reply, NewState} = Handler:count(DocName, HState),
   {reply, {OkOrError, Reply}, State#state{handler_state = NewState}};
 
+handle_call(
+  {count_by, DocName, Conditions}, _From,
+  #state{handler = Handler, handler_state = HState} = State
+) ->
+  {OkOrError, Reply, NewState} = Handler:count_by(DocName, Conditions, HState),
+  {reply, {OkOrError, Reply}, State#state{handler_state = NewState}};
+
 handle_call(
   {call, DocName, Function, Args}, _From,
   #state{handler = Handler, handler_state = HState} = State

test/sumo_basic_SUITE.erl

@@ -20,6 +20,7 @@
     delete/1,
     check_proper_dates/1,
     count/1,
+    count_by/1,
     persist_using_changeset/1
   ]}
 ]).