Only put non-toplevel vars into the INTO variable in a COLLECT.

This restores the behaviour of 2.2.

arangod/Aql/ExecutionBlock.cpp

@@ -2405,13 +2405,17 @@ AggregateBlock::AggregateBlock (ExecutionEngine* engine,
     }
 
     // iterate over all our variables
-    for (auto it = en->getRegisterPlan()->varInfo.begin(); 
-         it != en->getRegisterPlan()->varInfo.end(); ++it) {
-      // find variable in the global variable map
-      auto itVar = en->_variableMap.find((*it).first);
+    for (auto& vi : en->getRegisterPlan()->varInfo) {
+      if (vi.second.depth > 0 || en->getDepth() == 1) {
+        // Do not keep variables from depth 0, unless we are depth 1 ourselves
+        // (which means no FOR in which we are contained)
+ 
+        // find variable in the global variable map
+        auto itVar = en->_variableMap.find(vi.first);
 
-      if (itVar != en->_variableMap.end()) {
-        _variableNames[(*it).second.registerId] = (*itVar).second;
+        if (itVar != en->_variableMap.end()) {
+          _variableNames[vi.second.registerId] = (*itVar).second;
+        }
       }
     }
   }

arangod/Aql/ExecutionNode.cpp

@@ -2043,22 +2043,35 @@ ExecutionNode* AggregateNode::clone (ExecutionPlan* plan,
 ////////////////////////////////////////////////////////////////////////////////
 
 struct UserVarFinder : public WalkerWorker<ExecutionNode> {
-  UserVarFinder () {};
+  UserVarFinder (int mindepth) : mindepth(mindepth), depth(-1) {};
   ~UserVarFinder () {};
   std::vector<Variable const*> userVars;
+  int mindepth;   // minimal depth to consider
+  int depth;
 
   bool enterSubquery (ExecutionNode*, ExecutionNode*) override final {
     return false;
   }
 
-  bool before (ExecutionNode* en) override final {
-    auto vars = en->getVariablesSetHere();
-    for (auto v : vars) {
-      if (v->isUserDefined()) {
-        userVars.push_back(v);
+  void after (ExecutionNode* en) override final {
+    if (en->getType() == ExecutionNode::SINGLETON) {
+      depth = 0;
+    }
+    else if (en->getType() == ExecutionNode::ENUMERATE_COLLECTION ||
+             en->getType() == ExecutionNode::INDEX_RANGE ||
+             en->getType() == ExecutionNode::ENUMERATE_LIST ||
+             en->getType() == ExecutionNode::AGGREGATE) {
+      depth += 1;
+    }
+    // Now depth is set correct for this node.
+    if (depth >= mindepth) {
+      auto vars = en->getVariablesSetHere();
+      for (auto v : vars) {
+        if (v->isUserDefined()) {
+          userVars.push_back(v);
+        }
       }
     }
-    return false;
   }
 };
 
@@ -2069,10 +2082,18 @@ std::vector<Variable const*> AggregateNode::getVariablesUsedHere () const {
   }
   if (_outVariable != nullptr) {
     // Here we have to find all user defined variables in this query
-    // amonst our dependencies:
-    UserVarFinder finder;
+    // amongst our dependencies:
+    UserVarFinder finder(1);
     auto myselfasnonconst = const_cast<AggregateNode*>(this);
     myselfasnonconst->walk(&finder);
+    if (finder.depth == 1) {
+      // we are toplevel, let's run again with mindepth = 0
+      finder.userVars.clear();
+      finder.mindepth = 0;
+      finder.depth = -1;
+      finder.reset();
+      myselfasnonconst->walk(&finder);
+    }
     for (auto x : finder.userVars) {
       v.insert(x);
     }