NewIterators in read-only mode

Summary: As title.

Test Plan: Added test to column_family_test

Reviewers: ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20523

db/column_family_test.cc

@@ -857,6 +857,7 @@ TEST(ColumnFamilyTest, NewIteratorsTest) {
 TEST(ColumnFamilyTest, ReadOnlyDBTest) {
   Open();
   CreateColumnFamiliesAndReopen({"one", "two", "three", "four"});
+  ASSERT_OK(Put(0, "a", "b"));
   ASSERT_OK(Put(1, "foo", "bla"));
   ASSERT_OK(Put(2, "foo", "blabla"));
   ASSERT_OK(Put(3, "foo", "blablabla"));
@@ -870,6 +871,29 @@ TEST(ColumnFamilyTest, ReadOnlyDBTest) {
   ASSERT_EQ("bla", Get(1, "foo"));
   ASSERT_EQ("blablablabla", Get(2, "foo"));
 
+
+  // test newiterators
+  {
+    std::vector<Iterator*> iterators;
+    ASSERT_OK(db_->NewIterators(ReadOptions(), handles_, &iterators));
+    for (auto it : iterators) {
+      it->SeekToFirst();
+    }
+    ASSERT_EQ(IterStatus(iterators[0]), "a->b");
+    ASSERT_EQ(IterStatus(iterators[1]), "foo->bla");
+    ASSERT_EQ(IterStatus(iterators[2]), "foo->blablablabla");
+    for (auto it : iterators) {
+      it->Next();
+    }
+    ASSERT_EQ(IterStatus(iterators[0]), "(invalid)");
+    ASSERT_EQ(IterStatus(iterators[1]), "(invalid)");
+    ASSERT_EQ(IterStatus(iterators[2]), "(invalid)");
+
+    for (auto it : iterators) {
+      delete it;
+    }
+  }
+
   Close();
   // can't open dropped column family
   Status s = OpenReadOnly({"default", "one", "two"});

db/db_impl_readonly.cc

@@ -76,12 +76,42 @@ Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options,
   auto cfd = cfh->cfd();
   SuperVersion* super_version = cfd->GetSuperVersion()->Ref();
   SequenceNumber latest_snapshot = versions_->LastSequence();
-  Iterator* internal_iter = NewInternalIterator(options, cfd, super_version);
-  return NewDBIterator(
-      env_, *cfd->options(), cfd->user_comparator(), internal_iter,
+  auto db_iter = NewArenaWrappedDbIterator(
+      env_, *cfd->options(), cfd->user_comparator(),
       (options.snapshot != nullptr
            ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
            : latest_snapshot));
+  auto internal_iter =
+      NewInternalIterator(options, cfd, super_version, db_iter->GetArena());
+  db_iter->SetIterUnderDBIter(internal_iter);
+  return db_iter;
+}
+
+Status DBImplReadOnly::NewIterators(
+    const ReadOptions& options,
+    const std::vector<ColumnFamilyHandle*>& column_families,
+    std::vector<Iterator*>* iterators) {
+  if (iterators == nullptr) {
+    return Status::InvalidArgument("iterators not allowed to be nullptr");
+  }
+  iterators->clear();
+  iterators->reserve(column_families.size());
+  SequenceNumber latest_snapshot = versions_->LastSequence();
+
+  for (auto cfh : column_families) {
+    auto cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(cfh)->cfd();
+    auto db_iter = NewArenaWrappedDbIterator(
+        env_, *cfd->options(), cfd->user_comparator(),
+        options.snapshot != nullptr
+            ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
+            : latest_snapshot);
+    auto internal_iter = NewInternalIterator(
+        options, cfd, cfd->GetSuperVersion()->Ref(), db_iter->GetArena());
+    db_iter->SetIterUnderDBIter(internal_iter);
+    iterators->push_back(db_iter);
+  }
+
+  return Status::OK();
 }
 
 Status DB::OpenForReadOnly(const Options& options, const std::string& dbname,

db/db_impl_readonly.h

@@ -42,11 +42,8 @@ class DBImplReadOnly : public DBImpl {
 
   virtual Status NewIterators(
       const ReadOptions& options,
-      const std::vector<ColumnFamilyHandle*>& column_family,
-      std::vector<Iterator*>* iterators) {
-   // TODO
-    return Status::NotSupported("Not supported yet.");
-  }
+      const std::vector<ColumnFamilyHandle*>& column_families,
+      std::vector<Iterator*>* iterators);
 
   using DBImpl::Put;
   virtual Status Put(const WriteOptions& options,