From e4b3acbd11cb1e199b9c36860683d8fd1b35019a Mon Sep 17 00:00:00 2001
From: Gregory Burd <greg@basho.com>
Date: Wed, 13 Mar 2013 17:27:00 -0400
Subject: [PATCH] Share per-table cursors for get/put/delete operations.

---
 src/riak_kv_wterl_backend.erl | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/riak_kv_wterl_backend.erl b/src/riak_kv_wterl_backend.erl
index f536489..4f9e0bd 100644
--- a/src/riak_kv_wterl_backend.erl
+++ b/src/riak_kv_wterl_backend.erl
@@ -53,6 +53,7 @@
 -record(state, {conn :: wterl:connection(),
                 table :: string(),
                 session :: wterl:session(),
+		cursors :: ets:tid(),
                 partition :: integer()}).
 
 -type state() :: #state{}.
@@ -145,18 +146,24 @@ start(Partition, Config) ->
 
 %% @doc Stop the wterl backend
 -spec stop(state()) -> ok.
-stop(#state{conn=ConnRef, session=SRef}) ->
+stop(#state{conn=ConnRef, session=SRef, cursors=undefined}) ->
     ok = wterl:session_close(SRef),
-    wterl_conn:close(ConnRef).
+    wterl_conn:close(ConnRef);
+stop(#state{cursors=Cursors}=State) ->
+    ets:foldl(fun({_Table, Cursor}, _) ->
+		      ok = wterl:cursor_close(Cursor)
+              end, true, Cursors),
+    ets:delete(Cursors),
+    stop(State#state{cursors=undefined}).
 
 %% @doc Retrieve an object from the wterl backend
 -spec get(riak_object:bucket(), riak_object:key(), state()) ->
                  {ok, any(), state()} |
                  {ok, not_found, state()} |
                  {error, term(), state()}.
-get(Bucket, Key, #state{table=Table, session=SRef}=State) ->
+get(Bucket, Key, #state{session=SRef, table=Table}=State) ->
     WTKey = to_object_key(Bucket, Key),
-    case wterl:session_get(SRef, Table, WTKey) of
+    case wterl:cursor_search(shared_cursor(SRef, Table, State), WTKey) of
         {ok, Value} ->
             {ok, Value, State};
         not_found  ->
@@ -175,7 +182,7 @@ get(Bucket, Key, #state{table=Table, session=SRef}=State) ->
                  {error, term(), state()}.
 put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{table=Table, session=SRef}=State) ->
     WTKey = to_object_key(Bucket, PrimaryKey),
-    case wterl:session_put(SRef, Table, WTKey, Val) of
+    case wterl:cursor_insert(shared_cursor(SRef, Table, State), WTKey, Val) of
         ok ->
             {ok, State};
         {error, Reason} ->
@@ -191,7 +198,7 @@ put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{table=Table, session=SRef}=Stat
                     {error, term(), state()}.
 delete(Bucket, Key, _IndexSpecs, #state{table=Table, session=SRef}=State) ->
     WTKey = to_object_key(Bucket, Key),
-    case wterl:session_delete(SRef, Table, WTKey) of
+    case wterl:cursor_remove(shared_cursor(SRef, Table, State), WTKey) of
         ok ->
             {ok, State};
         {error, Reason} ->
@@ -340,6 +347,20 @@ callback(_Ref, _Msg, State) ->
 %% Internal functions
 %% ===================================================================
 
+shared_cursor(SRef, Table, #state{cursors=undefined}=State) ->
+    Cursors = ets:new(?MODULE, []),
+    shared_cursor(SRef, Table, State#state{cursors=Cursors});
+shared_cursor(SRef, Table, #state{cursors=Cursors}=State) ->
+    case ets:lookup(Cursors, Table) of
+	[{Table, Cursor}] ->
+	    {Cursor, State};
+	_ ->
+	    Cursor = wterl:cursor_open(SRef, Table),
+	    ets:insert(Cursors, {Table, Cursor}),
+	    {Cursor, State}
+    end.
+    
+
 %% @private
 %% Return a function to fold over the buckets on this backend
 fold_buckets_fun(FoldBucketsFun) ->