Remove env_ from MergingIterator

Summary: env_ is not used. Compiling for iOS complains.

Test Plan: compiles now

Reviewers: ljin, haobo, sdong, dhruba

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17589

db/db_impl.cc

@@ -1238,7 +1238,7 @@ Status DBImpl::WriteLevel0Table(ColumnFamilyData* cfd,
           (unsigned long)m->GetNextLogNumber());
       memtables.push_back(m->NewIterator());
     }
-    Iterator* iter = NewMergingIterator(env_, &cfd->internal_comparator(),
+    Iterator* iter = NewMergingIterator(&cfd->internal_comparator(),
                                         &memtables[0], memtables.size());
     Log(options_.info_log, "Level-0 flush table #%lu: started",
         (unsigned long)meta.number);
@@ -3211,9 +3211,8 @@ Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
   // Collect iterators for files in L0 - Ln
   super_version->current->AddIterators(options, storage_options_,
                                        &iterator_list);
-  Iterator* internal_iter =
+  Iterator* internal_iter = NewMergingIterator(
-      NewMergingIterator(env_, &cfd->internal_comparator(), &iterator_list[0],
+      &cfd->internal_comparator(), &iterator_list[0], iterator_list.size());
-                         iterator_list.size());
 
   IterState* cleanup = new IterState(this, &mutex_, super_version);
   internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, nullptr);
@@ -3262,8 +3261,8 @@ std::pair<Iterator*, Iterator*> DBImpl::GetTailingIteratorPair(
   std::vector<Iterator*> list;
   super_version->imm->AddIterators(options, &list);
   super_version->current->AddIterators(options, storage_options_, &list);
-  Iterator* immutable_iter = NewMergingIterator(
+  Iterator* immutable_iter =
-      env_, &cfd->internal_comparator(), &list[0], list.size());
+      NewMergingIterator(&cfd->internal_comparator(), &list[0], list.size());
 
   // create a DBIter that only uses memtable content; see NewIterator()
   immutable_iter =

db/version_set.cc

@@ -2617,7 +2617,7 @@ Iterator* VersionSet::MakeInputIterator(Compaction* c) {
   }
   assert(num <= space);
   Iterator* result = NewMergingIterator(
-      env_, &c->column_family_data()->internal_comparator(), list, num);
+      &c->column_family_data()->internal_comparator(), list, num);
   delete[] list;
   return result;
 }

table/merger.cc

@@ -25,16 +25,14 @@ namespace {
 
 class MergingIterator : public Iterator {
  public:
-  MergingIterator(Env* const env, const Comparator* comparator,
+  MergingIterator(const Comparator* comparator, Iterator** children, int n)
-                  Iterator** children, int n)
       : comparator_(comparator),
         children_(n),
         current_(nullptr),
         use_heap_(true),
-        env_(env),
         direction_(kForward),
         maxHeap_(NewMaxIterHeap(comparator_)),
-        minHeap_ (NewMinIterHeap(comparator_)) {
+        minHeap_(NewMinIterHeap(comparator_)) {
     for (int i = 0; i < n; i++) {
       children_[i].Set(children[i]);
     }
@@ -230,7 +228,6 @@ class MergingIterator : public Iterator {
   // This flag is always true for reverse direction, as we always use heap for
   // the reverse iterating case.
   bool use_heap_;
-  Env* const env_;
   // Which direction is the iterator moving?
   enum Direction {
     kForward,

table/merger.h

@@ -23,8 +23,7 @@ class Env;
 // key is present in K child iterators, it will be yielded K times.
 //
 // REQUIRES: n >= 0
-extern Iterator* NewMergingIterator(Env* const env,
+extern Iterator* NewMergingIterator(const Comparator* comparator,
-                                    const Comparator* comparator,
                                     Iterator** children, int n);
 
 }  // namespace rocksdb