From 1d4e5e1c8a700523fa5558334025a28f5087dc45 Mon Sep 17 00:00:00 2001
From: jsteemann <jan@arangodb.com>
Date: Thu, 24 Nov 2016 13:45:38 +0100
Subject: [PATCH] fixed array index behavior on hash collisions

---
 arangod/Indexes/HashIndex.cpp | 4 +++-
 arangod/Indexes/HashIndex.h   | 6 ++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arangod/Indexes/HashIndex.cpp b/arangod/Indexes/HashIndex.cpp
index 0e0fe8e7c3..c8c39efa72 100644
--- a/arangod/Indexes/HashIndex.cpp
+++ b/arangod/Indexes/HashIndex.cpp
@@ -233,6 +233,7 @@ static bool IsEqualElementElementMulti(void* userData,
     VPackSlice rightData = right->slice(context, i);
 
     int res = arangodb::basics::VelocyPackHelper::compare(leftData, rightData, false);
+
     if (res != 0) {
       return false;
     }
@@ -263,6 +264,7 @@ static bool IsEqualKeyElementMulti(void* userData,
     VPackSlice const rightVPack = right->slice(context, i);
   
     int res = arangodb::basics::VelocyPackHelper::compare(leftVPack, rightVPack, false);
+
     if (res != 0) {
       return false;
     }
@@ -480,7 +482,7 @@ HashIndex::HashIndex(TRI_idx_iid_t iid, LogicalCollection* collection,
   }
 
   auto func = std::make_unique<HashElementFunc>();
-  auto compare = std::make_unique<IsEqualElementElementByKey>(_paths.size());
+  auto compare = std::make_unique<IsEqualElementElementByKey>(_paths.size(), _useExpansion);
 
   if (_unique) {
     auto array = std::make_unique<TRI_HashArray_t>(
diff --git a/arangod/Indexes/HashIndex.h b/arangod/Indexes/HashIndex.h
index 8680b51a25..2e0eeac8bd 100644
--- a/arangod/Indexes/HashIndex.h
+++ b/arangod/Indexes/HashIndex.h
@@ -244,16 +244,17 @@ class HashIndex final : public PathBasedIndex {
   /// @brief determines if a key corresponds to an element
   class IsEqualElementElementByKey {
     size_t _numFields;
+    bool _allowExpansion;
 
    public:
-    explicit IsEqualElementElementByKey(size_t n) : _numFields(n) {}
+    IsEqualElementElementByKey(size_t n, bool allowExpansion) : _numFields(n), _allowExpansion(allowExpansion) {}
 
     bool operator()(void* userData, HashIndexElement const* left,
                     HashIndexElement const* right) {
       TRI_ASSERT(left->revisionId() != 0);
       TRI_ASSERT(right->revisionId() != 0);
 
-      if (left->revisionId() == right->revisionId()) {
+      if (!_allowExpansion && left->revisionId() == right->revisionId()) {
         return true;
       }
 
@@ -264,6 +265,7 @@ class HashIndex final : public PathBasedIndex {
         VPackSlice rightData = right->slice(context, i);
 
         int res = arangodb::basics::VelocyPackHelper::compare(leftData, rightData, false);
+
         if (res != 0) {
           return false;
         }