From 801c957348f78e9daec4cda76b968509a4aca8a9 Mon Sep 17 00:00:00 2001
From: Jan <jsteemann@users.noreply.github.com>
Date: Wed, 3 Jul 2019 16:15:15 +0200
Subject: [PATCH] add initializeCursor back to DistinctCollectExecutor (#9386)

---
 arangod/Aql/DistinctCollectExecutor.cpp | 21 +++++++++++++++------
 arangod/Aql/DistinctCollectExecutor.h   |  3 +++
 arangod/Aql/ExecutionBlockImpl.cpp      |  3 +++
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/arangod/Aql/DistinctCollectExecutor.cpp b/arangod/Aql/DistinctCollectExecutor.cpp
index 22eefcc548..8d40cebb51 100644
--- a/arangod/Aql/DistinctCollectExecutor.cpp
+++ b/arangod/Aql/DistinctCollectExecutor.cpp
@@ -64,12 +64,11 @@ DistinctCollectExecutor::DistinctCollectExecutor(Fetcher& fetcher, Infos& infos)
             AqlValueGroupEqual(_infos.getTransaction())) {}
 
 DistinctCollectExecutor::~DistinctCollectExecutor() {
-  // destroy all AqlValues captured
-  for (auto& it : _seen) {
-    for (auto& it2 : it) {
-      const_cast<AqlValue*>(&it2)->destroy();
-    }
-  }
+  destroyValues();
+}
+
+void DistinctCollectExecutor::initializeCursor() {
+  destroyValues();
 }
 
 std::pair<ExecutionState, NoStats> DistinctCollectExecutor::produceRows(OutputAqlItemRow& output) {
@@ -138,3 +137,13 @@ std::pair<ExecutionState, size_t> DistinctCollectExecutor::expectedNumberOfRows(
   // but it is upper bounded by the input.
   return _fetcher.preFetchNumberOfRows(atMost);
 }
+
+void DistinctCollectExecutor::destroyValues() {
+  // destroy all AqlValues captured
+  for (auto& it : _seen) {
+    for (auto& it2 : it) {
+      const_cast<AqlValue*>(&it2)->destroy();
+    }
+  }
+  _seen.clear();
+}
diff --git a/arangod/Aql/DistinctCollectExecutor.h b/arangod/Aql/DistinctCollectExecutor.h
index 2a2c322d76..f14349a3ff 100644
--- a/arangod/Aql/DistinctCollectExecutor.h
+++ b/arangod/Aql/DistinctCollectExecutor.h
@@ -95,6 +95,8 @@ class DistinctCollectExecutor {
   DistinctCollectExecutor(DistinctCollectExecutor const&) = delete;
   DistinctCollectExecutor(Fetcher& fetcher, Infos&);
   ~DistinctCollectExecutor();
+  
+  void initializeCursor();
 
   /**
    * @brief produce the next Row of Aql Values.
@@ -107,6 +109,7 @@ class DistinctCollectExecutor {
 
  private:
   Infos const& infos() const noexcept { return _infos; };
+  void destroyValues();
 
  private:
   Infos const& _infos;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 7c8272f041..e0e79ce64b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -372,6 +372,9 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor
   static_assert(!std::is_same<Executor, IndexExecutor>::value || customInit,
                 "IndexExecutor is expected to implement a custom "
                 "initializeCursor method!");
+  static_assert(!std::is_same<Executor, DistinctCollectExecutor>::value || customInit,
+                "DistinctCollectExecutor is expected to implement a custom "
+                "initializeCursor method!");
   InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
 
   // // use this with c++17 instead of specialisation below