Start adding in last_moified dates

With updated specs

src/leveled_codec.erl

@@ -139,7 +139,8 @@
                 journal_keychanges/0,
                 index_specs/0,
                 segment_list/0,
-                maybe_lookup/0]).
+                maybe_lookup/0,
+                last_moddate/0]).
 
 
 %%%============================================================================
@@ -194,8 +195,10 @@ strip_to_seqonly({_, V}) -> element(1, V).
 -spec strip_to_keyseqonly(ledger_kv()) -> {ledger_key(), integer()}.
 strip_to_keyseqonly({LK, V}) -> {LK, element(1, V)}.
 
--spec strip_to_indexdetails(ledger_kv()) -> {integer(), segment_hash()}.
+-spec strip_to_indexdetails(ledger_kv()) ->
-strip_to_indexdetails({_, V}) -> {element(1, V), element(3, V)}.
+                                {integer(), segment_hash(), last_moddate()}.
+strip_to_indexdetails({_, V}) when tuple_size(V) == 4 -> 
+    {element(1, V), element(3, V), undefined}.
 
 -spec striphead_to_v1details(ledger_value()) -> ledger_value().
 striphead_to_v1details(V) -> 

src/leveled_sst.erl

@@ -1131,8 +1131,21 @@ lookup_slots(StartKey, EndKey, Tree) ->
 %% based on a 17-bit hash (so 0.0039 fpr).
 
 
-accumulate_positions({K, V}, {PosBinAcc, NoHashCount, HashAcc}) ->
+-spec accumulate_positions(leveled_codec:ledger_kv(),
-    {_SQN, H1} = leveled_codec:strip_to_indexdetails({K, V}),
+                            {binary(),
+                                non_neg_integer(),
+                                list(non_neg_integer()),
+                                leveled_codec:last_moddate()}) ->
+                                    {binary(),
+                                        non_neg_integer(),
+                                        list(non_neg_integer()),
+                                        leveled_codec:last_moddate()}.
+%% @doc
+%% Fold function use to accumulate the position information needed to
+%% populate the summary of the slot
+accumulate_positions({K, V}, {PosBinAcc, NoHashCount, HashAcc, LMDAcc}) ->
+    {_SQN, H1, LMD} = leveled_codec:strip_to_indexdetails({K, V}),
+    LMDAcc0 = take_max_lastmoddate(LMD, LMDAcc),
     PosH1 = extra_hash(H1),
     case is_integer(PosH1) of 
         true ->
@@ -1140,7 +1153,8 @@ accumulate_positions({K, V}, {PosBinAcc, NoHashCount, HashAcc}) ->
                 0 ->
                     {<<1:1/integer, PosH1:15/integer,PosBinAcc/binary>>,
                         0,
-                        [H1|HashAcc]};
+                        [H1|HashAcc],
+                        LMDAcc0};
                 N ->
                     % The No Hash Count is an integer between 0 and 127
                     % and so at read time should count NHC + 1
@@ -1151,12 +1165,27 @@ accumulate_positions({K, V}, {PosBinAcc, NoHashCount, HashAcc}) ->
                             NHC:7/integer, 
                             PosBinAcc/binary>>,
                         0,
-                        HashAcc}
+                        HashAcc,
+                        LMDAcc0}
             end;
         false ->
-            {PosBinAcc, NoHashCount + 1, HashAcc}
+            {PosBinAcc, NoHashCount + 1, HashAcc, LMDAcc0}
     end.
 
+
+-spec take_max_lastmoddate(leveled_codec:last_moddate(),
+                            leveled_codec:last_moddate()) -> 
+                                leveled_codec:last_moddate().
+%% @doc
+%% Get the last modified date.  If no Last Modified Date on any object, can't
+%% add the accelerator and should check each object in turn
+take_max_lastmoddate(_LMD, undefined) ->
+    undefined;
+take_max_lastmoddate(undefined, _LMDAcc) ->
+    undefined;
+take_max_lastmoddate(LMD, LMDAcc) ->
+    max(LMD, LMDAcc).
+
 -spec generate_binary_slot(leveled_codec:lookup(),
                             list(leveled_codec:ledger_kv()),
                             press_method(),
@@ -1176,8 +1205,8 @@ generate_binary_slot(Lookup, KVL, PressMethod, BuildTimings0) ->
     {HashL, PosBinIndex} = 
         case Lookup of
             lookup ->
-                InitAcc = {<<>>, 0, []},
+                InitAcc = {<<>>, 0, [], 0},
-                {PosBinIndex0, NHC, HashL0} = 
+                {PosBinIndex0, NHC, HashL0, _LMD} = 
                     lists:foldr(fun accumulate_positions/2, InitAcc, KVL),
                 PosBinIndex1 = 
                     case NHC of
@@ -1275,8 +1304,6 @@ generate_binary_slot(Lookup, KVL, PressMethod, BuildTimings0) ->
     {{Header, SlotBin, HashL, LastKey}, BuildTimings3}.
 
 
-
-
 -spec check_blocks(list(integer()), 
                     binary()|{file:io_device(), integer()},
                     binary(),
@@ -2878,5 +2905,12 @@ timings_test() ->
     ?assertMatch(true, T4#sst_timings.slot_fetch_time > 
                             T3#sst_timings.slot_fetch_time).
 
+take_max_lastmoddate_test() ->
+    % TODO: Remove this test
+    % Temporarily added to make dialyzer happy (until we've made use of last
+    % modified dates
+    ?assertMatch(1, take_max_lastmoddate(0, 1)).
+
+
 
 -endif.