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diff --git a/src/couchdb/couch_key_tree.erl b/src/couchdb/couch_key_tree.erl
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+++ b/src/couchdb/couch_key_tree.erl
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+%   Copyright 2007, 2008 Damien Katz <damien_katz@yahoo.com>
+%
+%   Licensed under the Apache License, Version 2.0 (the "License");
+%   you may not use this file except in compliance with the License.
+%   You may obtain a copy of the License at
+%
+%       http://www.apache.org/licenses/LICENSE-2.0
+%
+%   Unless required by applicable law or agreed to in writing, software
+%   distributed under the License is distributed on an "AS IS" BASIS,
+%   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%   See the License for the specific language governing permissions and
+%   limitations under the License.
+
+-module(couch_key_tree).
+
+-export([merge/2, find_missing/2, get_key_leafs/2, get_full_key_paths/2, get/2]).
+-export([map/2, get_all_leafs/1, get_leaf_keys/1, count_leafs/1]).
+
+% a key tree looks like this:
+% Tree -> [] or [{Key, Value, Tree} | SiblingTree]
+% ChildTree -> Tree
+% SiblingTree -> [] or [{SiblingKey, Value, Tree} | Tree]
+% And each Key < SiblingKey
+
+
+
+% key tree functions
+
+% When the same key is found in the trees, the value in tree B is discarded.
+merge([], B) ->
+    B;
+merge(A, []) ->
+    A;
+merge([ATree | ANextTree], [BTree | BNextTree]) ->
+    {AKey, AValue, ASubTree} = ATree,
+    {BKey, _BValue, BSubTree} = BTree,
+    if
+    AKey == BKey ->
+        %same key
+        MergedSubTree = merge(ASubTree, BSubTree),
+        MergedNextTree = merge(ANextTree, BNextTree),
+        [{AKey, AValue, MergedSubTree} | MergedNextTree];
+    AKey < BKey ->
+        [ATree | merge(ANextTree, [BTree | BNextTree])];
+    true ->
+        [BTree | merge([ATree | ANextTree], BNextTree)]
+    end.
+
+find_missing(_Tree, []) ->
+    [];
+find_missing([], Keys) ->
+    Keys;
+find_missing([{Key, _, SubTree} | RestTree], Keys) ->
+    SrcKeys2 = Keys -- Key,
+    SrcKeys3 = find_missing(SubTree, SrcKeys2),
+    find_missing(RestTree, SrcKeys3).
+    
+
+% get the leafs in the tree matching the keys. The matching key nodes can be
+% leafs or an inner nodes. If an inner node, then the leafs for that node
+% are returned.
+get_key_leafs(Tree, Keys) ->
+    get_key_leafs(Tree, Keys, []).
+    
+get_key_leafs(_Tree, [], _KeyPathAcc) ->
+    {[], []};
+get_key_leafs([], KeysToGet, _KeyPathAcc) ->
+    {[], KeysToGet};
+get_key_leafs([{Key, _Value, SubTree}=Tree | RestTree], KeysToGet, KeyPathAcc) ->
+    case KeysToGet -- [Key] of
+    KeysToGet -> % same list, key not found    
+        {LeafsFound, KeysToGet2} = get_key_leafs(SubTree, KeysToGet, [Key | KeyPathAcc]),
+        {RestLeafsFound, KeysRemaining} = get_key_leafs(RestTree, KeysToGet2, KeyPathAcc),
+        {LeafsFound ++ RestLeafsFound, KeysRemaining};
+    KeysToGet2 ->
+        LeafsFound = get_all_leafs([Tree], KeyPathAcc),
+        LeafKeysFound = [LeafKeyFound || {LeafKeyFound, _, _} <- LeafsFound],
+        KeysToGet2 = KeysToGet2 -- LeafKeysFound,
+        {RestLeafsFound, KeysRemaining} = get_key_leafs(RestTree, KeysToGet2, KeyPathAcc),
+        {LeafsFound ++ RestLeafsFound, KeysRemaining}
+    end.
+
+get(Tree, KeysToGet) ->
+    {KeyPaths, KeysNotFound} = get_full_key_paths(Tree, KeysToGet),
+    FixedResults = [ {Key, Value, [Key0 || {Key0, _} <- Path]} || [{Key, Value}|_] = Path <- KeyPaths],
+    {FixedResults, KeysNotFound}.
+
+get_full_key_paths(Tree, Keys) ->
+    get_full_key_paths(Tree, Keys, []).
+    
+get_full_key_paths(_Tree, [], _KeyPathAcc) ->
+    {[], []};
+get_full_key_paths([], KeysToGet, _KeyPathAcc) ->
+    {[], KeysToGet};
+get_full_key_paths([{KeyId, Value, SubTree} | RestTree], KeysToGet, KeyPathAcc) ->
+    KeysToGet2 = KeysToGet -- [KeyId],
+    CurrentNodeResult =
+    case length(KeysToGet2) == length(KeysToGet) of
+    true -> % not in the key list.
+        [];
+    false -> % this node is the key list. return it
+        [[{KeyId, Value} | KeyPathAcc]]
+    end,
+    {KeysGotten, KeysRemaining} = get_full_key_paths(SubTree, KeysToGet2, [{KeyId, Value} | KeyPathAcc]),
+    {KeysGotten2, KeysRemaining2} = get_full_key_paths(RestTree, KeysRemaining, KeyPathAcc),
+    {CurrentNodeResult ++ KeysGotten ++ KeysGotten2, KeysRemaining2}.
+
+get_all_leafs(Tree) ->
+    get_all_leafs(Tree, []).
+    
+get_all_leafs([], _KeyPathAcc) ->
+    [];
+get_all_leafs([{KeyId, Value, []} | RestTree], KeyPathAcc) ->
+    [{KeyId, Value, [KeyId | KeyPathAcc]} | get_all_leafs(RestTree, KeyPathAcc)];
+get_all_leafs([{KeyId, _Value, SubTree} | RestTree], KeyPathAcc) ->
+    get_all_leafs(SubTree, [KeyId | KeyPathAcc]) ++ get_all_leafs(RestTree, KeyPathAcc).
+
+get_leaf_keys([]) ->
+    [];
+get_leaf_keys([{Key, _Value, []} | RestTree]) ->
+    [Key | get_leaf_keys(RestTree)];
+get_leaf_keys([{_Key, _Value, SubTree} | RestTree]) ->
+    get_leaf_keys(SubTree) ++ get_leaf_keys(RestTree).
+    
+count_leafs([]) ->
+    0;
+count_leafs([{_Key, _Value, []} | RestTree]) ->
+    1 + count_leafs(RestTree);
+count_leafs([{_Key, _Value, SubTree} | RestTree]) ->
+    count_leafs(SubTree) + count_leafs(RestTree).
+    
+
+map(_Fun, []) ->
+    [];
+map(Fun, [{Key, Value, SubTree} | RestTree]) ->
+    Value2 = Fun(Key, Value),
+    [{Key, Value2, map(Fun, SubTree)} | map(Fun, RestTree)].
+