added flag for disabling query tracking `--database.disable-query-tracking`

Conflicts:
	arangod/RestServer/ArangoServer.cpp

Conflicts:
	Documentation/Books/Users/ConfigureArango/Arangod.mdpp
	arangod/RestServer/ArangoServer.cpp

Documentation/Books/Users/ConfigureArango/Arangod.mdpp

@@ -94,6 +94,10 @@ the option *--disable-figures*.
 @startDocuBlock databaseForceSyncProperties
 
 
+!SUBSECTION Disable AQL query tracking
+@startDocuBlock databaseDisableQueryTracking
+
+
 !SUBSECTION Index threads
 @startDocuBlock indexThreads
 

arangod/Aql/ExecutionBlock.cpp

@@ -694,13 +694,18 @@ EnumerateCollectionBlock::EnumerateCollectionBlock (ExecutionEngine* engine,
     _atBeginning(false),
     _random(ep->_random) {
 
+  auto trxCollection = _trx->trxCollection(_collection->cid());
+  if (trxCollection != nullptr) {
+    _trx->orderBarrier(trxCollection);
+  }
+
   if (_random) {
     // random scan
-    _scanner = new RandomCollectionScanner(_trx, _trx->trxCollection(_collection->cid()));
+    _scanner = new RandomCollectionScanner(_trx, trxCollection);
   }
   else {
     // default: linear scan
-    _scanner = new LinearCollectionScanner(_trx, _trx->trxCollection(_collection->cid()));
+    _scanner = new LinearCollectionScanner(_trx, trxCollection);
   }
 }
 
@@ -913,6 +918,11 @@ IndexRangeBlock::IndexRangeBlock (ExecutionEngine* engine,
     _sortCoords(),
     _freeCondition(true) {
 
+  auto trxCollection = _trx->trxCollection(_collection->cid());
+  if (trxCollection != nullptr) {
+    _trx->orderBarrier(trxCollection);
+  }
+     
   for (size_t i = 0; i < en->_ranges.size(); i++) {
     _condition->emplace_back(IndexAndCondition());
     for (auto ri: en->_ranges[i]) {
@@ -3576,6 +3586,11 @@ ModificationBlock::ModificationBlock (ExecutionEngine* engine,
     _outReg(ExecutionNode::MaxRegisterId),
     _collection(ep->_collection) {
   
+  auto trxCollection = _trx->trxCollection(_collection->cid());
+  if (trxCollection != nullptr) {
+    _trx->orderBarrier(trxCollection);
+  }
+
   if (ep->_outVariable != nullptr) {
     /*
     auto const& registerPlan = ep->getRegisterPlan()->varInfo;

arangod/Aql/Query.cpp

@@ -86,11 +86,14 @@ Profile::Profile (Query* query)
     stamp(TRI_microtime()) {
 
   auto queryList = static_cast<QueryList*>(query->vocbase()->_queries);
+
+  if (queryList != nullptr) {
     try {
       queryList->insert(query, stamp);
     }
     catch (...) {
     }
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -99,7 +102,14 @@ Profile::Profile (Query* query)
       
 Profile::~Profile () { 
   auto queryList = static_cast<QueryList*>(query->vocbase()->_queries);
+
+  if (queryList != nullptr) {
+    try {
       queryList->remove(query, stamp);
+    }
+    catch (...) {
+    }
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -134,6 +144,12 @@ TRI_json_t* Profile::toJson (TRI_memory_zone_t*) {
 // --SECTION--                                                       class Query
 // -----------------------------------------------------------------------------
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief whether or not query tracking is disabled globally
+////////////////////////////////////////////////////////////////////////////////
+          
+bool Query::DoDisableQueryTracking = false;
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                        constructors / destructors
 // -----------------------------------------------------------------------------

arangod/Aql/Query.h

@@ -504,6 +504,22 @@ namespace triagens {
 
         triagens::arango::TransactionContext* createTransactionContext ();
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief fetch the global query tracking value
+////////////////////////////////////////////////////////////////////////////////
+
+        static bool DisableQueryTracking () {
+          return DoDisableQueryTracking;
+        }
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief turn off tracking globally
+////////////////////////////////////////////////////////////////////////////////
+        
+        static void DisableQueryTracking (bool value) {
+          DoDisableQueryTracking = value;
+        }
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                                 private variables
 // -----------------------------------------------------------------------------
@@ -663,6 +679,12 @@ namespace triagens {
 
         bool                              _killed;
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief whether or not query tracking is disabled globally
+////////////////////////////////////////////////////////////////////////////////
+          
+        static bool DoDisableQueryTracking;
+
     };
 
   }

arangod/Aql/QueryList.cpp

@@ -82,7 +82,7 @@ QueryList::QueryList (TRI_vocbase_t*)
     _current(),
     _slow(),
     _slowCount(0),
-    _enabled(true),
+    _enabled(! Query::DisableQueryTracking()),
     _trackSlowQueries(true),
     _slowQueryThreshold(QueryList::DefaultSlowQueryThreshold),
     _maxSlowQueries(QueryList::DefaultMaxSlowQueries),
@@ -116,7 +116,7 @@ QueryList::~QueryList () {
 void QueryList::insert (Query const* query,
                         double stamp) {
   // no query string
-  if (query->queryString() == nullptr || ! _enabled) {
+  if (! _enabled || query == nullptr || query->queryString() == nullptr) {
     return;
   }
 
@@ -140,7 +140,7 @@ void QueryList::insert (Query const* query,
 void QueryList::remove (Query const* query,
                         double now) {
   // no query string
-  if (query->queryString() == nullptr || ! _enabled) {
+  if (! _enabled || query == nullptr || query->queryString() == nullptr) {
     return;
   }
 

arangod/RestServer/ArangoServer.cpp

@@ -36,6 +36,7 @@
 #include "Admin/ApplicationAdminServer.h"
 #include "Admin/RestHandlerCreator.h"
 #include "Admin/RestShutdownHandler.h"
+#include "Aql/Query.h"
 #include "Basics/FileUtils.h"
 #include "Basics/Nonce.h"
 #include "Basics/ProgramOptions.h"
@@ -288,6 +289,7 @@ ArangoServer::ArangoServer (int argc, char** argv)
     _defaultWaitForSync(false),
     _forceSyncProperties(true),
     _disableReplicationApplier(false),
+    _disableQueryTracking(false),
     _server(nullptr),
     _queryRegistry(nullptr),
     _pairForAql(nullptr),
@@ -530,6 +532,7 @@ void ArangoServer::buildApplicationServer () {
     ("database.maximal-journal-size", &_defaultMaximalSize, "default maximal journal size, can be overwritten when creating a collection")
     ("database.wait-for-sync", &_defaultWaitForSync, "default wait-for-sync behavior, can be overwritten when creating a collection")
     ("database.force-sync-properties", &_forceSyncProperties, "force syncing of collection properties to disk, will use waitForSync value of collection when turned off")
+    ("database.disable-query-tracking", &_disableQueryTracking, "turn off AQL query tracking by default")
     ("database.index-threads", &_indexThreads, "threads to start for parallel background index creation")
   ;
 
@@ -672,6 +675,10 @@ void ArangoServer::buildApplicationServer () {
     _disableAuthentication = true;
   }
   
+  // set global query tracking flag
+  triagens::aql::Query::DisableQueryTracking(_disableQueryTracking);
+
+
   // .............................................................................
   // now run arangod
   // .............................................................................

arangod/RestServer/ArangoServer.h

@@ -470,6 +470,19 @@ namespace triagens {
 
         bool _disableReplicationApplier;
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief disable the query tracking feature
+/// @startDocuBlock databaseDisableQueryTracking
+/// `--database.disable-query-tracking flag`
+///
+/// If *true*, the server's query tracking feature will be disabled by default.
+///
+/// The default is *false*.
+/// @endDocuBlock
+////////////////////////////////////////////////////////////////////////////////
+
+        bool _disableQueryTracking;
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief unit tests
 ///

js/server/tests/aql-queries-collection.js

@@ -127,6 +127,17 @@ function ahuacatlQueryCollectionTestSuite () {
       internal.db._drop("UnitTestsAhuacatlUserRelations");
     },
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief return a single value as part of a document
+////////////////////////////////////////////////////////////////////////////////
+
+    testFilterEmpty : function () {
+      var expected = [ ];
+      var actual = getQueryResults("FOR u in " + users.name() + " FILTER u.id < 0 SORT u.id RETURN { \"name\" : u.name }");
+
+      assertEqual(expected, actual);
+    },
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief return a single value as part of a document
 ////////////////////////////////////////////////////////////////////////////////