IndexedDB: Optimize range deletion operations (e.g. clearing a store)

content/browser/indexed_db/leveldb/leveldb_transaction.cc

Index: content/browser/indexed_db/leveldb/leveldb_transaction.cc
diff --git a/content/browser/indexed_db/leveldb/leveldb_transaction.cc b/content/browser/indexed_db/leveldb/leveldb_transaction.cc
index 016e7dea72b90ed23f1247f28813119d1f615f56..76a7403ba5b2e91928040a3c36c8157918bd60cc 100644
--- a/content/browser/indexed_db/leveldb/leveldb_transaction.cc
+++ b/content/browser/indexed_db/leveldb/leveldb_transaction.cc
@@ -25,7 +25,7 @@ LevelDBTransaction::LevelDBTransaction(LevelDBDatabase* db)
       data_(data_comparator_),
       finished_(false) {}
 
-LevelDBTransaction::Record::Record() : deleted(false) {}
+LevelDBTransaction::Record::Record() {}
 LevelDBTransaction::Record::~Record() {}
 
 LevelDBTransaction::~LevelDBTransaction() {}
@@ -60,6 +60,29 @@ bool LevelDBTransaction::Remove(const StringPiece& key) {
   return !Set(key, &empty, true);
 }
 
+leveldb::Status LevelDBTransaction::RemoveRange(const StringPiece& begin,
+                                                const StringPiece& end,
+                                                bool upper_open) {
+  IDB_TRACE("LevelDBTransaction::RemoveRange");
+  data_.erase(data_.lower_bound(begin), data_.lower_bound(end));
+  if (!upper_open)
+    data_.erase(end);
+  std::unique_ptr<LevelDBIterator> it = CreateIterator();
+  leveldb::Status s;
+  for (s = it->Seek(begin);
+       s.ok() && it->IsValid() &&
+       (upper_open ? comparator_->Compare(it->Key(), end) < 0
+                   : comparator_->Compare(it->Key(), end) <= 0);
+       s = it->Next()) {
+    std::unique_ptr<Record> record = base::MakeUnique<Record>();
+    record->key = it->Key().as_string();
+    record->deleted = true;
+    data_[record->key] = std::move(record);
+  }
+  NotifyIterators();
+  return s;
+}
+
 leveldb::Status LevelDBTransaction::Get(const StringPiece& key,
                                         std::string* value,
                                         bool* found) {