From 958d3f5e14b7c835ecdda37c3bf78cf352b6f593 Mon Sep 17 00:00:00 2001
From: Martin Sumner <martin.sumner@adaptip.co.uk>
Date: Mon, 4 Dec 2017 09:29:44 +0000
Subject: [PATCH] Revert "Disable compression L0 and L1"

This reverts commit b10c0cf895e5d2ead8cf90a57de4057cd4375cfb.
---
 src/leveled_sst.erl | 37 ++++++++-----------------------------
 1 file changed, 8 insertions(+), 29 deletions(-)

diff --git a/src/leveled_sst.erl b/src/leveled_sst.erl
index 1cd5267..f080f19 100644
--- a/src/leveled_sst.erl
+++ b/src/leveled_sst.erl
@@ -81,7 +81,6 @@
 -define(CACHE_SIZE, 32).
 -define(BLOCK_LENGTHS_LENGTH, 20).
 -define(FLIPPER32, 4294967295).
--define(COMPRESS_AT_LEVEL, 2).
 
 -include_lib("eunit/include/eunit.hrl").
 
@@ -127,7 +126,7 @@
                         size :: integer(),
                         max_sqn :: integer()}).
 
--type press_methods() :: lz4|native|none.
+-type press_methods() :: lz4|native.
 
 %% yield_blockquery is used to detemrine if the work necessary to process a
 %% range query beyond the fetching the slot should be managed from within
@@ -205,8 +204,7 @@ sst_open(RootPath, Filename) ->
 %% lists as merge_lists will not be called.
 sst_new(RootPath, Filename, Level, KVList, MaxSQN, PressMethod) ->
     {ok, Pid} = gen_fsm:start(?MODULE, [], []),
-    PressMethod0 = compress_level(Level, PressMethod),
-    {[], [], SlotList, FK}  = merge_lists(KVList, PressMethod0),
+    {[], [], SlotList, FK}  = merge_lists(KVList, PressMethod),
     case gen_fsm:sync_send_event(Pid,
                                     {sst_new,
                                         RootPath,
@@ -214,7 +212,7 @@ sst_new(RootPath, Filename, Level, KVList, MaxSQN, PressMethod) ->
                                         Level,
                                         {SlotList, FK},
                                         MaxSQN,
-                                        PressMethod0},
+                                        PressMethod},
                                     infinity) of
         {ok, {SK, EK}, Bloom} ->
             {ok, Pid, {SK, EK}, Bloom}
@@ -237,9 +235,8 @@ sst_new(RootPath, Filename, Level, KVList, MaxSQN, PressMethod) ->
 sst_new(RootPath, Filename, 
         KVL1, KVL2, IsBasement, Level, 
         MaxSQN, PressMethod) ->
-    PressMethod0 = compress_level(Level, PressMethod),
     {Rem1, Rem2, SlotList, FK} = 
-        merge_lists(KVL1, KVL2, {IsBasement, Level}, PressMethod0),
+        merge_lists(KVL1, KVL2, {IsBasement, Level}, PressMethod),
     case SlotList of
         [] ->
             empty;
@@ -252,7 +249,7 @@ sst_new(RootPath, Filename,
                                                 Level,
                                                 {SlotList, FK},
                                                 MaxSQN,
-                                                PressMethod0},
+                                                PressMethod},
                                             infinity) of
                 {ok, {SK, EK}, Bloom} ->
                     {ok, Pid, {{Rem1, Rem2}, SK, EK}, Bloom}
@@ -270,7 +267,6 @@ sst_new(RootPath, Filename,
 sst_newlevelzero(RootPath, Filename, 
                     Slots, FetchFun, Penciller,
                     MaxSQN, PressMethod) ->
-    PressMethod0 = compress_level(0, PressMethod),
     {ok, Pid} = gen_fsm:start(?MODULE, [], []),
     gen_fsm:send_event(Pid,
                         {sst_newlevelzero,
@@ -280,7 +276,7 @@ sst_newlevelzero(RootPath, Filename,
                             FetchFun,
                             Penciller,
                             MaxSQN,
-                            PressMethod0}),
+                            PressMethod}),
     {ok, Pid, noreply}.
 
 -spec sst_get(pid(), tuple()) -> tuple()|not_present.
@@ -791,13 +787,6 @@ fetch_range(StartKey, EndKey, ScanWidth, SegList, State) ->
                     State#state.compression_method),
     {SlotsToFetchBinList, SlotsToPoint}.
 
--spec compress_level(integer(), press_methods()) -> press_methods().
-%% @doc
-%% disable compression at higher levels for improved performance
-compress_level(Level, _PressMethod) when Level < ?COMPRESS_AT_LEVEL ->
-    none;
-compress_level(_Level, PressMethod) ->
-    PressMethod.
 
 write_file(RootPath, Filename, SummaryBin, SlotsBin, PressMethod) ->
     SummaryLength = byte_size(SummaryBin),
@@ -843,14 +832,10 @@ read_file(Filename, State) ->
         Bloom}.
 
 gen_fileversion(PressMethod) ->
-    % Native or none can be treated the same once written, as reader 
-    % does not need to know as compression info will be in header of the 
-    % block
     Bit1 = 
         case PressMethod of 
             lz4 -> 1;
-            native -> 0;
-            none -> 0
+            native -> 0
         end,
     Bit1.
 
@@ -960,10 +945,6 @@ serialise_block(Term, lz4) ->
 serialise_block(Term, native) ->
     Bin = term_to_binary(Term, ?BINARY_SETTINGS),
     CRC32 = hmac(Bin),
-    <<Bin/binary, CRC32:32/integer>>;
-serialise_block(Term, none) ->
-    Bin = term_to_binary(Term),
-    CRC32 = hmac(Bin),
     <<Bin/binary, CRC32:32/integer>>.
 
 
@@ -987,12 +968,10 @@ deserialise_block(Bin, PressMethod) ->
 deserialise_checkedblock(Bin, lz4) ->
     {ok, Bin0} = lz4:unpack(Bin),
     binary_to_term(Bin0);
-deserialise_checkedblock(Bin, _Other) ->
-    % native or none can be treated the same
+deserialise_checkedblock(Bin, native) ->
     binary_to_term(Bin).
 
 
-
 -spec hmac(binary()|integer()) -> integer().
 %% @doc
 %% Perform a CRC check on an input