diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index b2c7545823..9bc447ca6f 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -67,11 +67,6 @@ void ExecutionBlock::walk (WalkerWorker* worker) {
   worker->after(this);
 }
 
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief
-////////////////////////////////////////////////////////////////////////////////
-
 // Local Variables:
 // mode: outline-minor
 // outline-regexp: "^\\(/// @brief\\|/// {@inheritDoc}\\|/// @addtogroup\\|// --SECTION--\\|/// @\\}\\)"
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index d69d395229..0c4ed97548 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -594,7 +594,7 @@ namespace triagens {
 ////////////////////////////////////////////////////////////////////////////////
 
         ~EnumerateCollectionBlock () {
-          if (_allDocs.size() > 0) {
+          if (! _allDocs.empty()) {
             for (auto it = _allDocs.begin(); it != _allDocs.end(); ++it) {
               delete *it;
             }
@@ -627,6 +627,7 @@ namespace triagens {
 
           auto shaper = trx.documentCollection()->getShaper();
 
+          // TODO: if _allDocs is not empty, its contents will leak
           _allDocs.clear();
           for (size_t i = 0; i < n; ++i) {
             TRI_shaped_json_t shaped;
@@ -637,7 +638,7 @@ namespace triagens {
           
           res = trx.finish(res);
 
-          if (_allDocs.size() == 0) {
+          if (_allDocs.empty()) {
             _done = true;
           }
 
@@ -653,7 +654,7 @@ namespace triagens {
           if (res != TRI_ERROR_NO_ERROR) {
             return res;
           }
-          if (_allDocs.size() == 0) {
+          if (_allDocs.empty()) {
             _done = true;
           }
           return TRI_ERROR_NO_ERROR;
@@ -773,7 +774,7 @@ namespace triagens {
 
       private:
 
-        vector<Json*> _allDocs;
+        std::vector<Json*> _allDocs;
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief current position in _allDocs
@@ -783,19 +784,19 @@ namespace triagens {
     };
 
 // -----------------------------------------------------------------------------
-// --SECTION--                                                         RootBlock
+// --SECTION--                                                       ReturnBlock
 // -----------------------------------------------------------------------------
 
-    class RootBlock : public ExecutionBlock {
+    class ReturnBlock : public ExecutionBlock {
 
       public:
 
-        RootBlock (RootNode const* ep)
+        ReturnBlock (ReturnNode const* ep)
           : ExecutionBlock(ep) {
 
         }
 
-        ~RootBlock () {
+        ~ReturnBlock () {
         } 
 
         virtual AqlItemBlock* getOne () {
@@ -808,7 +809,7 @@ namespace triagens {
 
           // Let's steal the actual result and throw away the vars:
           AqlItemBlock* stripped = new AqlItemBlock(1, 1);
-          auto ep = static_cast<RootNode const*>(getPlanNode());
+          auto ep = static_cast<ReturnNode const*>(getPlanNode());
           auto it = _varOverview->varInfo.find(ep->_inVariable->id);
           TRI_ASSERT(it != _varOverview->varInfo.end());
           unsigned int index = it->second.index;
@@ -826,7 +827,7 @@ namespace triagens {
           }
 
           // Let's steal the actual result and throw away the vars:
-          auto ep = static_cast<RootNode const*>(getPlanNode());
+          auto ep = static_cast<ReturnNode const*>(getPlanNode());
           auto it = _varOverview->varInfo.find(ep->_inVariable->id);
           TRI_ASSERT(it != _varOverview->varInfo.end());
           unsigned int index = it->second.index;
diff --git a/arangod/Aql/ExecutionEngine.cpp b/arangod/Aql/ExecutionEngine.cpp
index a69dc5b3ae..d3823ceb45 100644
--- a/arangod/Aql/ExecutionEngine.cpp
+++ b/arangod/Aql/ExecutionEngine.cpp
@@ -88,7 +88,7 @@ struct Instanciator : public ExecutionNode::WalkerWorker {
         break;
       }
       case ExecutionNode::ROOT: {
-        eb = new RootBlock(static_cast<RootNode const*>(en));
+        eb = new ReturnBlock(static_cast<ReturnNode const*>(en));
         root = eb;
         break;
       }
@@ -138,14 +138,13 @@ ExecutionEngine* ExecutionEngine::instanciateFromPlan (ExecutionNode* plan) {
     root->initialize();
 
     engine->_root = root;
-
+  
+    return engine;
   }
   catch (...) {
     delete engine;
     throw;
   }
-
-  return engine;
 }
 
 // -----------------------------------------------------------------------------
diff --git a/arangod/Aql/ExecutionNode.cpp b/arangod/Aql/ExecutionNode.cpp
index 667f17b373..987251eee0 100644
--- a/arangod/Aql/ExecutionNode.cpp
+++ b/arangod/Aql/ExecutionNode.cpp
@@ -414,16 +414,16 @@ void AggregateOnUnsortedNode::toJsonHelper (std::map<ExecutionNode*, int>& index
 }
 
 // -----------------------------------------------------------------------------
-// --SECTION--                                               methods of RootNode
+// --SECTION--                                             methods of ReturnNode
 // -----------------------------------------------------------------------------
 
 ////////////////////////////////////////////////////////////////////////////////
-/// @brief toJson, for RootNode
+/// @brief toJson, for ReturnNode
 ////////////////////////////////////////////////////////////////////////////////
 
-void RootNode::toJsonHelper (std::map<ExecutionNode*, int>& indexTab,
-                             triagens::basics::Json& nodes,
-                             TRI_memory_zone_t* zone) {
+void ReturnNode::toJsonHelper (std::map<ExecutionNode*, int>& indexTab,
+                               triagens::basics::Json& nodes,
+                               TRI_memory_zone_t* zone) {
   Json json(ExecutionNode::toJsonHelperGeneric(indexTab, nodes, zone));  // call base class method
   if (json.isEmpty()) {
     return;
diff --git a/arangod/Aql/ExecutionNode.h b/arangod/Aql/ExecutionNode.h
index 917bd4c0cd..256ddb70b0 100644
--- a/arangod/Aql/ExecutionNode.h
+++ b/arangod/Aql/ExecutionNode.h
@@ -1073,17 +1073,17 @@ namespace triagens {
 
 
 // -----------------------------------------------------------------------------
-// --SECTION--                                                    class RootNode
+// --SECTION--                                                  class ReturnNode
 // -----------------------------------------------------------------------------
 
 ////////////////////////////////////////////////////////////////////////////////
-/// @brief class RootNode, derived from ExecutionNode
+/// @brief class ReturnNode, derived from ExecutionNode
 ////////////////////////////////////////////////////////////////////////////////
 
-    class RootNode : public ExecutionNode {
+    class ReturnNode : public ExecutionNode {
       
       friend class ExecutionBlock;
-      friend class RootBlock;
+      friend class ReturnBlock;
       
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief constructors for various arguments, always with offset and limit
@@ -1091,7 +1091,7 @@ namespace triagens {
 
       public:
 
-        RootNode (Variable const* inVariable)
+        ReturnNode (Variable const* inVariable)
           : ExecutionNode(), _inVariable(inVariable) {
 
           TRI_ASSERT(_inVariable != nullptr);
@@ -1110,7 +1110,7 @@ namespace triagens {
 ////////////////////////////////////////////////////////////////////////////////
 
         virtual std::string getTypeString () const {
-          return std::string("RootNode");
+          return std::string("ReturnNode");
         }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1126,7 +1126,7 @@ namespace triagens {
 ////////////////////////////////////////////////////////////////////////////////
 
         virtual ExecutionNode* clone () const {
-          auto c = new RootNode(_inVariable);
+          auto c = new ReturnNode(_inVariable);
           cloneDependencies(c);
           return static_cast<ExecutionNode*>(c);
         }
diff --git a/arangod/Aql/ExecutionPlan.cpp b/arangod/Aql/ExecutionPlan.cpp
index 4d4365bbca..1ac7c09885 100644
--- a/arangod/Aql/ExecutionPlan.cpp
+++ b/arangod/Aql/ExecutionPlan.cpp
@@ -96,13 +96,20 @@ ExecutionPlan* ExecutionPlan::instanciateFromAst (Ast const* ast) {
 // -----------------------------------------------------------------------------
 
 ////////////////////////////////////////////////////////////////////////////////
-/// @brief add a node to the plan
+/// @brief add a node to the plan, will delete node if addition fails
 ////////////////////////////////////////////////////////////////////////////////
 
-void ExecutionPlan::addNode (ExecutionNode* node) {
+ExecutionNode* ExecutionPlan::addNode (ExecutionNode* node) {
   TRI_ASSERT(node != nullptr);
 
-  _nodes.push_back(node);
+  try {
+    _nodes.push_back(node);
+    return node;
+  }
+  catch (...) {
+    delete node;
+    throw;
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -119,7 +126,10 @@ CalculationNode* ExecutionPlan::createTemporaryCalculation (Ast const* ast,
   auto expr = new Expression(ast->query()->executor(), const_cast<AstNode*>(expression));
 
   try {
-    return new CalculationNode(expr, out);
+    auto en = new CalculationNode(expr, out);
+
+    addNode(reinterpret_cast<ExecutionNode*>(en));
+    return en;
   }
   catch (...) {
     // prevent memleak
@@ -167,27 +177,27 @@ ExecutionNode* ExecutionPlan::fromNodeFor (Ast const* ast,
   auto v = static_cast<Variable*>(variable->getData());
   TRI_ASSERT(v != nullptr);
   
-  ExecutionNode* plan = nullptr;
+  ExecutionNode* en = nullptr;
 
   // peek at second operand
   if (expression->type == NODE_TYPE_COLLECTION) {
     // second operand is a collection
     char const* collectionName = expression->getStringValue();
-    plan = new EnumerateCollectionNode(ast->query()->vocbase(), std::string(collectionName), v);
+    en = addNode(new EnumerateCollectionNode(ast->query()->vocbase(), std::string(collectionName), v));
   }
   else if (expression->type == NODE_TYPE_REFERENCE) {
     // second operand is already a variable
     auto inVariable = static_cast<Variable*>(variable->getData());
     TRI_ASSERT(inVariable != nullptr);
-    plan = new EnumerateListNode(inVariable, v);
+    en = addNode(new EnumerateListNode(inVariable, v));
   }
   else {
     // second operand is some misc. expression
     auto calc = createTemporaryCalculation(ast, expression);
 
     try {
-      plan = new EnumerateListNode(calc->outVariable(), v);
-      plan->addDependency(calc);
+      en = addNode(new EnumerateListNode(calc->outVariable(), v));
+      en->addDependency(calc);
     }
     catch (...) {
       // prevent memleak
@@ -195,9 +205,9 @@ ExecutionNode* ExecutionPlan::fromNodeFor (Ast const* ast,
     }
   }
 
-  TRI_ASSERT(plan != nullptr);
+  TRI_ASSERT(en != nullptr);
   
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -212,21 +222,21 @@ ExecutionNode* ExecutionPlan::fromNodeFilter (Ast const* ast,
   
   auto expression = node->getMember(0);
 
-  ExecutionNode* plan = nullptr;
+  ExecutionNode* en = nullptr;
   
   if (expression->type == NODE_TYPE_REFERENCE) {
     // operand is already a variable
     auto v = static_cast<Variable*>(expression->getData());
     TRI_ASSERT(v != nullptr);
-    plan = new FilterNode(v);
+    en = addNode(new FilterNode(v));
   }
   else {
     // operand is some misc expression
     auto calc = createTemporaryCalculation(ast, expression);
 
     try {
-      plan = new FilterNode(calc->outVariable());
-      plan->addDependency(calc);
+      en = addNode(new FilterNode(calc->outVariable()));
+      en->addDependency(calc);
     }
     catch (...) {
       // prevent memleak
@@ -234,7 +244,7 @@ ExecutionNode* ExecutionPlan::fromNodeFilter (Ast const* ast,
     }
   }
 
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -252,7 +262,7 @@ ExecutionNode* ExecutionPlan::fromNodeLet (Ast const* ast,
 
   auto v = static_cast<Variable*>(variable->getData());
   
-  ExecutionNode* plan = nullptr;
+  ExecutionNode* en = nullptr;
 
   if (expression->type == NODE_TYPE_SUBQUERY) {
     // TODO: node might be a subquery. this is currently NOT handled
@@ -263,7 +273,7 @@ ExecutionNode* ExecutionPlan::fromNodeLet (Ast const* ast,
     auto expr = new Expression(ast->query()->executor(), const_cast<AstNode*>(expression));
 
     try {
-      plan = new CalculationNode(expr, v);
+      en = addNode(new CalculationNode(expr, v));
     }
     catch (...) {
       // prevent memleak
@@ -272,7 +282,7 @@ ExecutionNode* ExecutionPlan::fromNodeLet (Ast const* ast,
     }
   }
     
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -331,9 +341,9 @@ ExecutionNode* ExecutionPlan::fromNodeSort (Ast const* ast,
     previous = (*it);
   }
 
-  auto plan = new SortNode(elements);
+  auto en = addNode(new SortNode(elements));
 
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -370,9 +380,9 @@ ExecutionNode* ExecutionPlan::fromNodeLimit (Ast const* ast,
   TRI_ASSERT(offset->type == NODE_TYPE_VALUE);
   TRI_ASSERT(count->type == NODE_TYPE_VALUE);
 
-  auto plan = new LimitNode(static_cast<size_t>(offset->getIntValue()), static_cast<size_t>(count->getIntValue()));
+  auto en = addNode(new LimitNode(static_cast<size_t>(offset->getIntValue()), static_cast<size_t>(count->getIntValue())));
 
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -387,21 +397,21 @@ ExecutionNode* ExecutionPlan::fromNodeReturn (Ast const* ast,
   
   auto expression = node->getMember(0);
 
-  ExecutionNode* plan = nullptr;
+  ExecutionNode* en = nullptr;
   
   if (expression->type == NODE_TYPE_REFERENCE) {
     // operand is already a variable
     auto v = static_cast<Variable*>(expression->getData());
     TRI_ASSERT(v != nullptr);
-    plan = new RootNode(v);
+    en = addNode(new ReturnNode(v));
   }
   else {
     // operand is some misc expression
     auto calc = createTemporaryCalculation(ast, expression);
 
     try {
-      plan = new RootNode(calc->outVariable());
-      plan->addDependency(calc);
+      en = addNode(new ReturnNode(calc->outVariable()));
+      en->addDependency(calc);
     }
     catch (...) {
       // prevent memleak
@@ -409,7 +419,7 @@ ExecutionNode* ExecutionPlan::fromNodeReturn (Ast const* ast,
     }
   }
 
-  return addDependency(previous, plan);
+  return addDependency(previous, en);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -480,7 +490,7 @@ ExecutionNode* ExecutionPlan::fromNode (Ast const* ast,
                                         AstNode const* node) {
   TRI_ASSERT(node != nullptr);
 
-  ExecutionNode* plan = new SingletonNode();
+  ExecutionNode* en = addNode(new SingletonNode());
 
   try {
     size_t const n = node->numMembers();
@@ -494,78 +504,78 @@ ExecutionNode* ExecutionPlan::fromNode (Ast const* ast,
 
       switch (member->type) {
         case NODE_TYPE_FOR: {
-          plan = fromNodeFor(ast, plan, member);
+          en = fromNodeFor(ast, en, member);
           break;
         }
 
         case NODE_TYPE_FILTER: {
-          plan = fromNodeFilter(ast, plan, member);
+          en = fromNodeFilter(ast, en, member);
           break;
         }
 
         case NODE_TYPE_LET: {
-          plan = fromNodeLet(ast, plan, member);
+          en = fromNodeLet(ast, en, member);
           break;
         }
       
         case NODE_TYPE_SORT: {
-          plan = fromNodeSort(ast, plan, member);
+          en = fromNodeSort(ast, en, member);
           break;
         }
       
         case NODE_TYPE_COLLECT: {
-          plan = fromNodeCollect(ast, plan, member);
+          en = fromNodeCollect(ast, en, member);
           break;
         }
        
         case NODE_TYPE_LIMIT: {
-          plan = fromNodeLimit(ast, plan, member);
+          en = fromNodeLimit(ast, en, member);
           break;
         }
       
         case NODE_TYPE_RETURN: {
-          plan = fromNodeReturn(ast, plan, member);
+          en = fromNodeReturn(ast, en, member);
           break;
         }
       
         case NODE_TYPE_REMOVE: {
-          plan = fromNodeRemove(ast, plan, member);
+          en = fromNodeRemove(ast, en, member);
           break;
         }
       
         case NODE_TYPE_INSERT: {
-          plan = fromNodeInsert(ast, plan, member);
+          en = fromNodeInsert(ast, en, member);
           break;
         }
       
         case NODE_TYPE_UPDATE: {
-          plan = fromNodeUpdate(ast, plan, member);
+          en = fromNodeUpdate(ast, en, member);
           break;
         }
       
         case NODE_TYPE_REPLACE: {
-          plan = fromNodeReplace(ast, plan, member);
+          en = fromNodeReplace(ast, en, member);
           break;
         }
 
         default: {
           // node type not implemented
-          plan = nullptr;
+          en = nullptr;
           break;
         }
       }
 
-      if (plan == nullptr) {
+      if (en == nullptr) {
         THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
       }
     }
   
-    return plan;
+    return en;
   }
   catch (...) {
     // prevent memleak
-    if (plan != nullptr) {
-      delete plan;
+    if (en != nullptr) {
+      delete en;
     }
     throw;
   }
diff --git a/arangod/Aql/ExecutionPlan.h b/arangod/Aql/ExecutionPlan.h
index 177952f460..d97289366e 100644
--- a/arangod/Aql/ExecutionPlan.h
+++ b/arangod/Aql/ExecutionPlan.h
@@ -94,10 +94,10 @@ namespace triagens {
       private:
 
 ////////////////////////////////////////////////////////////////////////////////
-/// @brief add a node to the plan
+/// @brief add a node to the plan, will delete node if addition fails
 ////////////////////////////////////////////////////////////////////////////////
 
-        void addNode (ExecutionNode*);
+        ExecutionNode* addNode (ExecutionNode*);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief creates a calculation node for an arbitrary expression