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

content/browser/indexed_db/leveldb/leveldb_unittest.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 <stddef.h>
 
 #include <algorithm>
 #include <cstring>
 #include <string>
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/strings/string_piece.h"
 #include "content/browser/indexed_db/leveldb/leveldb_comparator.h"
 #include "content/browser/indexed_db/leveldb/leveldb_database.h"
 #include "content/browser/indexed_db/leveldb/leveldb_env.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/leveldatabase/env_chromium.h"
 
 namespace content {
 
 namespace {
+static const size_t kDefaultMaxOpenIteratorsPerDatabase = 50;
 
 class SimpleComparator : public LevelDBComparator {
  public:
   int Compare(const base::StringPiece& a,
               const base::StringPiece& b) const override {
     size_t len = std::min(a.size(), b.size());
     return memcmp(a.begin(), b.begin(), len);
   }
   const char* Name() const override { return "temp_comparator"; }
 };
 
 }  // namespace
 
 TEST(LevelDBDatabaseTest, CorruptionTest) {
   base::ScopedTempDir temp_directory;
   ASSERT_TRUE(temp_directory.CreateUniqueTempDir());
 
   const std::string key("key");
   const std::string value("value");
   std::string put_value;
   std::string got_value;
   SimpleComparator comparator;
 
   std::unique_ptr<LevelDBDatabase> leveldb;
-  LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb);
+  LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb,
+                        kDefaultMaxOpenIteratorsPerDatabase);
   EXPECT_TRUE(leveldb);
   put_value = value;
   leveldb::Status status = leveldb->Put(key, &put_value);
   EXPECT_TRUE(status.ok());
   leveldb.reset();
   EXPECT_FALSE(leveldb);
 
-  LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb);
+  LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb,
+                        kDefaultMaxOpenIteratorsPerDatabase);
   EXPECT_TRUE(leveldb);
   bool found = false;
   status = leveldb->Get(key, &got_value, &found);
   EXPECT_TRUE(status.ok());
   EXPECT_TRUE(found);
   EXPECT_EQ(value, got_value);
   leveldb.reset();
   EXPECT_FALSE(leveldb);
 
   base::FilePath file_path = temp_directory.GetPath().AppendASCII("CURRENT");
   base::File file(file_path, base::File::FLAG_OPEN | base::File::FLAG_WRITE);
   file.SetLength(0);
   file.Close();
 
-  status =
-      LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb);
+  status = LevelDBDatabase::Open(temp_directory.GetPath(), &comparator,
+                                 &leveldb, kDefaultMaxOpenIteratorsPerDatabase);
   EXPECT_FALSE(leveldb);
   EXPECT_FALSE(status.ok());
   EXPECT_TRUE(status.IsCorruption());
 
   status = LevelDBDatabase::Destroy(temp_directory.GetPath());
   EXPECT_TRUE(status.ok());
 
-  status =
-      LevelDBDatabase::Open(temp_directory.GetPath(), &comparator, &leveldb);
+  status = LevelDBDatabase::Open(temp_directory.GetPath(), &comparator,
+                                 &leveldb, kDefaultMaxOpenIteratorsPerDatabase);
   EXPECT_TRUE(status.ok());
   EXPECT_TRUE(leveldb);
   status = leveldb->Get(key, &got_value, &found);
   EXPECT_TRUE(status.ok());
   EXPECT_FALSE(found);
 }
 
 TEST(LevelDB, Locking) {
   base::ScopedTempDir temp_directory;
   ASSERT_TRUE(temp_directory.CreateUniqueTempDir());
@@ skipping 12 matching lines @@
 
   leveldb::FileLock* lock2;
   status = env->LockFile(file.AsUTF8Unsafe(), &lock2);
   EXPECT_FALSE(status.ok());
 
   status = env->UnlockFile(lock);
   EXPECT_TRUE(status.ok());
 }
 
 }  // namespace content