[IndexedDB] Pool and evict leveldb iterators, to save memory

content/browser/indexed_db/indexed_db_backing_store.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/indexed_db_backing_store.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/files/file_path.h"
@@ skipping 40 matching lines @@
 
 using base::FilePath;
 using base::StringPiece;
 using leveldb::Status;
 using storage::FileWriterDelegate;
 using url::Origin;
 
 namespace content {
 
 namespace {
+static const size_t kDefaultMaxOpenIteratorsPerDatabase = 50;

[pwnall, 2017/03/24 09:16:02]

How about explaining that we do this because every iterator hangs on to a
leveldb block, which can be large, and linking to http://crbug.com/696055?

[dmurph, 2017/03/24 23:33:39]

Done.

 
 enum IndexedDBBackingStoreErrorSource {
   // 0 - 2 are no longer used.
   FIND_KEY_IN_INDEX = 3,
   GET_IDBDATABASE_METADATA,
   GET_INDEXES,
   GET_KEY_GENERATOR_CURRENT_NUMBER,
   GET_OBJECT_STORES,
   GET_RECORD,
   KEY_EXISTS_IN_OBJECT_STORE,
@@ skipping 986 matching lines @@
 
 }  // namespace
 
 class DefaultLevelDBFactory : public LevelDBFactory {
  public:
   DefaultLevelDBFactory() {}
   Status OpenLevelDB(const FilePath& file_name,
                      const LevelDBComparator* comparator,
                      std::unique_ptr<LevelDBDatabase>* db,
                      bool* is_disk_full) override {
-    return LevelDBDatabase::Open(file_name, comparator, db, is_disk_full);
+    return LevelDBDatabase::Open(file_name, comparator, db,
+                                 kDefaultMaxOpenIteratorsPerDatabase,
+                                 is_disk_full);
   }
   Status DestroyLevelDB(const FilePath& file_name) override {
     return LevelDBDatabase::Destroy(file_name);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultLevelDBFactory);
 };
 
 IndexedDBBackingStore::IndexedDBBackingStore(
@@ skipping 3376 matching lines @@
 
 IndexedDBBackingStore::Transaction::WriteDescriptor::WriteDescriptor(
     const WriteDescriptor& other) = default;
 IndexedDBBackingStore::Transaction::WriteDescriptor::~WriteDescriptor() =
     default;
 IndexedDBBackingStore::Transaction::WriteDescriptor&
     IndexedDBBackingStore::Transaction::WriteDescriptor::
     operator=(const WriteDescriptor& other) = default;
 
 }  // namespace content