diff --git a/Ahuacatl/ahuacatl-access-optimizer.c b/Ahuacatl/ahuacatl-access-optimizer.c
index 020b8ee582..bbf12f8245 100644
--- a/Ahuacatl/ahuacatl-access-optimizer.c
+++ b/Ahuacatl/ahuacatl-access-optimizer.c
@@ -126,9 +126,6 @@ static void FreeAccess (TRI_aql_context_t* const context,
                         TRI_aql_field_access_t* const fieldAccess) {
   assert(fieldAccess);
 
-  // remove from hash first
-  TRI_RemoveKeyAssociativePointer(&context->_ranges, fieldAccess->_fieldName);
-
   FreeAccessMembers(fieldAccess);
   TRI_Free(TRI_UNKNOWN_MEM_ZONE, fieldAccess->_fieldName);
   TRI_Free(TRI_UNKNOWN_MEM_ZONE, fieldAccess);
@@ -300,7 +297,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
 
     FreeAccessMembers(lhs);
-    FreeAccessMembers(rhs);
+    FreeAccess(context, rhs);
 
     if (merged->_value._objects._length > 0) {
       // merged list is not empty
@@ -308,6 +305,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
     else {
       // merged list is empty
+      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, merged);
       lhs->_type = TRI_AQL_ACCESS_IMPOSSIBLE;
     }
 
@@ -341,7 +339,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
 
     FreeAccessMembers(lhs);
-    FreeAccessMembers(rhs);
+    FreeAccess(context, rhs);
 
     if (listInRange->_value._objects._length > 0) {
       // merged list is not empty
@@ -349,6 +347,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
     else {
       // merged list is empty
+      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, listInRange);
       lhs->_type = TRI_AQL_ACCESS_IMPOSSIBLE;
     }
 
@@ -373,7 +372,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
 
     FreeAccessMembers(lhs);
-    FreeAccessMembers(rhs);
+    FreeAccess(context, rhs);
 
     if (listInRange->_value._objects._length > 0) {
       // merged list is not empty
@@ -381,6 +380,7 @@ static TRI_aql_field_access_t* MergeAndList (TRI_aql_context_t* const context,
     }
     else {
       // merged list is empty
+      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, listInRange);
       lhs->_type = TRI_AQL_ACCESS_IMPOSSIBLE;
     }
 
@@ -929,7 +929,7 @@ static TRI_aql_field_access_t* MergeOrList (TRI_aql_context_t* const context,
     }
 
     FreeAccessMembers(lhs);
-    FreeAccessMembers(rhs);
+    FreeAccess(context, rhs);
 
     if (merged->_value._objects._length > 0) {
       // merged list is not empty
@@ -937,6 +937,7 @@ static TRI_aql_field_access_t* MergeOrList (TRI_aql_context_t* const context,
     }
     else {
       // merged list is empty
+      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, merged);
       lhs->_type = TRI_AQL_ACCESS_IMPOSSIBLE;
     }
 
@@ -1081,8 +1082,10 @@ static TRI_aql_field_access_t* MergeAccess (TRI_aql_context_t* const context,
                                             const TRI_aql_logical_e logicalType, 
                                             TRI_aql_field_access_t* lhs,
                                             TRI_aql_field_access_t* rhs) {
+  assert(context);
   assert(lhs);
   assert(rhs);
+  assert(logicalType == TRI_AQL_LOGICAL_AND || logicalType == TRI_AQL_LOGICAL_OR);
 
   assert(lhs->_fieldName != NULL);
   assert(rhs->_fieldName != NULL);
@@ -1146,6 +1149,7 @@ static TRI_aql_field_access_t* CreateAccessForNode (TRI_aql_context_t* const con
   TRI_aql_field_access_t* fieldAccess;
   TRI_json_t* value;
 
+  assert(context);
   assert(field);
   assert(field->_name._buffer);
   assert(node);
@@ -1232,6 +1236,9 @@ static void NoteAttributeAccess (TRI_aql_context_t* const context,
                                  const TRI_aql_node_t* const node) {
   TRI_aql_field_access_t* previous;
   TRI_aql_field_access_t* fieldAccess;
+  
+  assert(logicalType == TRI_AQL_LOGICAL_AND || logicalType == TRI_AQL_LOGICAL_OR);
+  assert(node);
 
   if (!field || !field->_name._buffer) {
     return;
@@ -1245,12 +1252,16 @@ static void NoteAttributeAccess (TRI_aql_context_t* const context,
   }
 
   // look up previous range first
-  previous = (TRI_aql_field_access_t*) TRI_LookupByKeyAssociativePointer(&context->_ranges, fieldAccess->_fieldName);
+  previous = (TRI_aql_field_access_t*) TRI_LookupByKeyAssociativePointer(context->_ranges, fieldAccess->_fieldName);
   if (previous) {
+    TRI_aql_field_access_t* merged;
     // previous range exists, now merge new access type with previous one
+    
+    // remove from hash first
+    TRI_RemoveKeyAssociativePointer(context->_ranges, fieldAccess->_fieldName);
 
     // MergeAccess() will free previous and/or fieldAccess
-    TRI_aql_field_access_t* merged = MergeAccess(context, logicalType, fieldAccess, previous);
+    merged = MergeAccess(context, logicalType, fieldAccess, previous);
     
     if (!merged) {
       // OOM
@@ -1258,11 +1269,11 @@ static void NoteAttributeAccess (TRI_aql_context_t* const context,
       return;
     }
 
-    TRI_InsertKeyAssociativePointer(&context->_ranges, merged->_fieldName, merged, true);
+    TRI_InsertKeyAssociativePointer(context->_ranges, merged->_fieldName, merged, true);
   }
   else {
     // no previous access exists, no need to merge
-    TRI_InsertKeyAssociativePointer(&context->_ranges, fieldAccess->_fieldName, fieldAccess, false);
+    TRI_InsertKeyAssociativePointer(context->_ranges, fieldAccess->_fieldName, fieldAccess, false);
   }
 }
 
@@ -1273,6 +1284,9 @@ static void NoteAttributeAccess (TRI_aql_context_t* const context,
 
 static TRI_aql_attribute_name_t* GetAttributeName (TRI_aql_context_t* const context,
                                                    const TRI_aql_node_t* const node) {
+  assert(context);
+  assert(node);
+
   if (node->_type == AQL_NODE_ATTRIBUTE_ACCESS) {
     TRI_aql_attribute_name_t* field = GetAttributeName(context, TRI_AQL_NODE_MEMBER(node, 0));
 
@@ -1309,6 +1323,70 @@ static TRI_aql_attribute_name_t* GetAttributeName (TRI_aql_context_t* const cont
 /// @}
 ////////////////////////////////////////////////////////////////////////////////
 
+// -----------------------------------------------------------------------------
+// --SECTION--                                        constructors / destructors
+// -----------------------------------------------------------------------------
+
+////////////////////////////////////////////////////////////////////////////////
+/// @addtogroup Ahuacatl
+/// @{
+////////////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief init the optimizer
+////////////////////////////////////////////////////////////////////////////////
+
+bool TRI_InitOptimizerAql (TRI_aql_context_t* const context) {
+  assert(context);
+  assert(context->_ranges == NULL);
+
+  context->_ranges = (TRI_associative_pointer_t*) TRI_Allocate(TRI_UNKNOWN_MEM_ZONE, sizeof(TRI_associative_pointer_t), false);
+  if (!context->_ranges) {
+    TRI_SetErrorContextAql(context, TRI_ERROR_OUT_OF_MEMORY, NULL);
+    return false;
+  }
+
+  TRI_InitAssociativePointer(context->_ranges,
+                             TRI_UNKNOWN_MEM_ZONE, 
+                             &TRI_HashStringKeyAssociativePointer, 
+                             &HashFieldAccess,
+                             &EqualFieldAccess,
+                             NULL);
+
+  return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief shutdown the optimizer
+////////////////////////////////////////////////////////////////////////////////
+
+void TRI_FreeOptimizerAql (TRI_aql_context_t* const context) {
+  assert(context);
+
+  if (context->_ranges) {
+    size_t i, n;
+
+    // free all remaining access elements
+    n = context->_ranges->_nrAlloc;
+    for (i = 0; i < n; ++i) {
+      TRI_aql_field_access_t* fieldAccess = (TRI_aql_field_access_t*) context->_ranges->_table[i];
+      if (!fieldAccess) {
+        continue;
+      }
+
+      FreeAccess(context, fieldAccess);
+    }
+
+    // free hash array
+    TRI_FreeAssociativePointer(TRI_UNKNOWN_MEM_ZONE, context->_ranges);
+    context->_ranges = NULL;
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+/// @}
+////////////////////////////////////////////////////////////////////////////////
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                                  public functions
 // -----------------------------------------------------------------------------
@@ -1324,9 +1402,11 @@ static TRI_aql_attribute_name_t* GetAttributeName (TRI_aql_context_t* const cont
 
 void TRI_DumpRangesAql (TRI_aql_context_t* const context) {
   size_t i; 
+  
+  assert(context);
    
-  for (i = 0; i < context->_ranges._nrAlloc; ++i) {
-    TRI_aql_field_access_t* fieldAccess = context->_ranges._table[i]; 
+  for (i = 0; i < context->_ranges->_nrAlloc; ++i) {
+    TRI_aql_field_access_t* fieldAccess = context->_ranges->_table[i]; 
 
     if (!fieldAccess) {
       continue;
@@ -1340,6 +1420,7 @@ void TRI_DumpRangesAql (TRI_aql_context_t* const context) {
       TRI_StringifyJson(&b, fieldAccess->_value._value);
 
       printf("- VALUE: %s\n", b._buffer);
+      TRI_DestroyStringBuffer(&b);
     }
     else if (fieldAccess->_type == TRI_AQL_ACCESS_RANGE_SINGLE) {
       TRI_string_buffer_t b;
@@ -1347,6 +1428,7 @@ void TRI_DumpRangesAql (TRI_aql_context_t* const context) {
       TRI_StringifyJson(&b, fieldAccess->_value._singleRange._value);
 
       printf("- VALUE: %s\n", b._buffer);
+      TRI_DestroyStringBuffer(&b);
     }
     else if (fieldAccess->_type == TRI_AQL_ACCESS_RANGE_DOUBLE) {
       TRI_string_buffer_t b;
@@ -1356,24 +1438,11 @@ void TRI_DumpRangesAql (TRI_aql_context_t* const context) {
       TRI_StringifyJson(&b, fieldAccess->_value._between._upper._value);
 
       printf("- VALUE: %s\n", b._buffer);
+      TRI_DestroyStringBuffer(&b);
     }
   }
 }
   
-////////////////////////////////////////////////////////////////////////////////
-/// @brief init the optimizer
-////////////////////////////////////////////////////////////////////////////////
-
-void TRI_InitOptimizerAql (TRI_aql_context_t* const context) {
-  // TODO: must free
-  TRI_InitAssociativePointer(&context->_ranges,
-                             TRI_UNKNOWN_MEM_ZONE, 
-                             &TRI_HashStringKeyAssociativePointer, 
-                             &HashFieldAccess,
-                             &EqualFieldAccess,
-                             NULL);
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief inspect a condition and note all accesses found for it
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/Ahuacatl/ahuacatl-access-optimizer.h b/Ahuacatl/ahuacatl-access-optimizer.h
index c3dc8e926d..17d22c8551 100644
--- a/Ahuacatl/ahuacatl-access-optimizer.h
+++ b/Ahuacatl/ahuacatl-access-optimizer.h
@@ -134,6 +134,31 @@ TRI_aql_attribute_name_t;
 /// @}
 ////////////////////////////////////////////////////////////////////////////////
 
+// -----------------------------------------------------------------------------
+// --SECTION--                                        constructors / destructors
+// -----------------------------------------------------------------------------
+
+////////////////////////////////////////////////////////////////////////////////
+/// @addtogroup Ahuacatl
+/// @{
+////////////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief init the optimizer
+////////////////////////////////////////////////////////////////////////////////
+
+bool TRI_InitOptimizerAql (TRI_aql_context_t* const);
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief shutdown the optimizer
+////////////////////////////////////////////////////////////////////////////////
+
+void TRI_FreeOptimizerAql (TRI_aql_context_t* const);
+
+////////////////////////////////////////////////////////////////////////////////
+/// @}
+////////////////////////////////////////////////////////////////////////////////
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                                  public functions
 // -----------------------------------------------------------------------------
@@ -149,12 +174,6 @@ TRI_aql_attribute_name_t;
 
 void TRI_DumpRangesAql (TRI_aql_context_t* const);
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief init the optimizer
-////////////////////////////////////////////////////////////////////////////////
-
-void TRI_InitOptimizerAql (TRI_aql_context_t* const);
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief inspect a condition and note all accesses found for it
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/Ahuacatl/ahuacatl-constant-folder.c b/Ahuacatl/ahuacatl-constant-folder.c
index b0b4615f06..ee67302e00 100644
--- a/Ahuacatl/ahuacatl-constant-folder.c
+++ b/Ahuacatl/ahuacatl-constant-folder.c
@@ -31,7 +31,7 @@
 
 #include "V8/v8-execution.h"
 
-#undef RANGE_OPTIMIZER 
+#undef RANGE_OPTIMIZER
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                                 private functions
@@ -660,7 +660,10 @@ TRI_aql_node_t* TRI_FoldConstantsAql (TRI_aql_context_t* const context,
   TRI_aql_modify_tree_walker_t* walker;
  
 #ifdef RANGE_OPTIMIZER  
-  TRI_InitOptimizerAql(context);
+  if (!TRI_InitOptimizerAql(context)) {
+    TRI_SetErrorContextAql(context, TRI_ERROR_OUT_OF_MEMORY, NULL);
+    return node;
+  }
 #endif
      
   walker = TRI_CreateModifyTreeWalkerAql((void*) context, &ModifyNode);
diff --git a/Ahuacatl/ahuacatl-context.c b/Ahuacatl/ahuacatl-context.c
index 471685d90b..ed245d983b 100644
--- a/Ahuacatl/ahuacatl-context.c
+++ b/Ahuacatl/ahuacatl-context.c
@@ -26,6 +26,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Ahuacatl/ahuacatl-context.h"
+#include "Ahuacatl/ahuacatl-access-optimizer.h"
 #include "Ahuacatl/ahuacatl-ast-node.h"
 #include "Ahuacatl/ahuacatl-bind-parameter.h"
 #include "Ahuacatl/ahuacatl-collections.h"
@@ -77,6 +78,8 @@ TRI_aql_context_t* TRI_CreateContextAql (TRI_vocbase_t* vocbase,
   }
 
   context->_vocbase = vocbase;
+  context->_ranges = NULL;
+
   context->_variableIndex = 0;
   
   // actual bind parameter values
@@ -161,6 +164,9 @@ void TRI_FreeContextAql (TRI_aql_context_t* const context) {
   }
   TRI_DestroyVectorPointer(&context->_scopes);
 
+  // free range optimizer
+  TRI_FreeOptimizerAql(context);
+
   // free all strings registered
   i = context->_strings._length;
   while (i--) {
diff --git a/Ahuacatl/ahuacatl-context.h b/Ahuacatl/ahuacatl-context.h
index a069040839..3890f93f83 100644
--- a/Ahuacatl/ahuacatl-context.h
+++ b/Ahuacatl/ahuacatl-context.h
@@ -82,7 +82,7 @@ typedef struct TRI_aql_context_s {
   TRI_associative_pointer_t _parameterValues;
   TRI_associative_pointer_t _parameterNames;
   TRI_associative_pointer_t _collectionNames;
-  TRI_associative_pointer_t _ranges;
+  TRI_associative_pointer_t* _ranges;
   size_t _variableIndex;
   void* _first;
   char* _query;
diff --git a/Ahuacatl/ahuacatl-conversions.c b/Ahuacatl/ahuacatl-conversions.c
index cb3c8a39b6..64a0bd3660 100644
--- a/Ahuacatl/ahuacatl-conversions.c
+++ b/Ahuacatl/ahuacatl-conversions.c
@@ -89,7 +89,12 @@ TRI_json_t* TRI_NodeJsonAql (TRI_aql_context_t* const context,
       if (result) {
         n = node->_members._length;
         for (i = 0; i < n; ++i) {
-          TRI_PushBackListJson(TRI_UNKNOWN_MEM_ZONE, result, TRI_NodeJsonAql(context, TRI_AQL_NODE_MEMBER(node, i)));
+          TRI_json_t* subValue = TRI_NodeJsonAql(context, TRI_AQL_NODE_MEMBER(node, i));
+
+          if (subValue) {
+            TRI_PushBack2ListJson(result, subValue); 
+            TRI_Free(TRI_UNKNOWN_MEM_ZONE, subValue);
+          }
         }
       }
       return result; 
@@ -102,7 +107,15 @@ TRI_json_t* TRI_NodeJsonAql (TRI_aql_context_t* const context,
         n = node->_members._length;
         for (i = 0; i < n; ++i) {
           TRI_aql_node_t* element = TRI_AQL_NODE_MEMBER(node, i);
-          TRI_InsertArrayJson(TRI_UNKNOWN_MEM_ZONE, result, TRI_AQL_NODE_STRING(element), TRI_NodeJsonAql(context, TRI_AQL_NODE_MEMBER(element, 0)));
+          TRI_json_t* subValue = TRI_NodeJsonAql(context, TRI_AQL_NODE_MEMBER(element, 0));
+
+          if (subValue) {
+            TRI_Insert2ArrayJson(TRI_UNKNOWN_MEM_ZONE, 
+                                 result, 
+                                 TRI_AQL_NODE_STRING(element), 
+                                 subValue);
+            TRI_Free(TRI_UNKNOWN_MEM_ZONE, subValue);
+          }
         }
       }
       return result; 
diff --git a/Ahuacatl/ahuacatl-error.c b/Ahuacatl/ahuacatl-error.c
index a442441161..649f070b07 100644
--- a/Ahuacatl/ahuacatl-error.c
+++ b/Ahuacatl/ahuacatl-error.c
@@ -141,6 +141,8 @@ char* TRI_GetContextErrorAql (const char* const query, const size_t line, const
   size_t currentLine = 1;
   size_t currentColumn = 1;
   const char* p = query;
+  char* temp;
+  char* result;
   size_t offset;
   char c;
  
@@ -169,7 +171,16 @@ char* TRI_GetContextErrorAql (const char* const query, const size_t line, const
     return TRI_DuplicateString2(query + offset, strlen(query) - offset);
   }
 
-  return TRI_Concatenate2String(TRI_DuplicateString2(query + offset, SNIPPET_LENGTH), SNIPPET_SUFFIX);
+  temp = TRI_DuplicateString2(query + offset, SNIPPET_LENGTH);
+  if (!temp) {
+    // out of memory
+    return NULL;
+  }
+
+  result = TRI_Concatenate2String(temp, SNIPPET_SUFFIX);
+  TRI_FreeString(TRI_CORE_MEM_ZONE, temp);
+
+  return result;
 }
 
 ////////////////////////////////////////////////////////////////////////////////