Componentize HistoryDatabase

chrome/browser/history/history_database.h

-// Copyright (c) 2012 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.
-
-#ifndef CHROME_BROWSER_HISTORY_HISTORY_DATABASE_H_
-#define CHROME_BROWSER_HISTORY_HISTORY_DATABASE_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "base/gtest_prod_util.h"
-#include "build/build_config.h"
-#include "components/history/core/browser/download_database.h"
-#include "components/history/core/browser/url_database.h"
-#include "components/history/core/browser/visit_database.h"
-#include "components/history/core/browser/visitsegment_database.h"
-#include "sql/connection.h"
-#include "sql/init_status.h"
-#include "sql/meta_table.h"
-
-#if defined(OS_ANDROID)
-#include "components/history/core/android/android_cache_database.h"
-#include "components/history/core/android/android_urls_database.h"
-#endif
-
-namespace base {
-class FilePath;
-}
-
-class HistoryQuickProviderTest;
-
-namespace history {
-
-// Encapsulates the SQL connection for the history database. This class holds
-// the database connection and has methods the history system (including full
-// text search) uses for writing and retrieving information.
-//
-// We try to keep most logic out of the history database; this should be seen
-// as the storage interface. Logic for manipulating this storage layer should
-// be in HistoryBackend.cc.
-class HistoryDatabase : public DownloadDatabase,
-#if defined(OS_ANDROID)
-                        public AndroidURLsDatabase,
-                        public AndroidCacheDatabase,
-#endif
-                        public URLDatabase,
-                        public VisitDatabase,
-                        public VisitSegmentDatabase {
- public:
-  // A simple class for scoping a history database transaction. This does not
-  // support rollback since the history database doesn't, either.
-  class TransactionScoper {
-   public:
-    explicit TransactionScoper(HistoryDatabase* db) : db_(db) {
-      db_->BeginTransaction();
-    }
-    ~TransactionScoper() {
-      db_->CommitTransaction();
-    }
-   private:
-    HistoryDatabase* db_;
-  };
-
-  // Must call Init() to complete construction. Although it can be created on
-  // any thread, it must be destructed on the history thread for proper
-  // database cleanup.
-  HistoryDatabase();
-
-  ~HistoryDatabase() override;
-
-  // Call before Init() to set the error callback to be used for the
-  // underlying database connection.
-  void set_error_callback(
-      const sql::Connection::ErrorCallback& error_callback) {
-    error_callback_ = error_callback;
-  }
-
-  // Must call this function to complete initialization. Will return
-  // sql::INIT_OK on success. Otherwise, no other function should be called. You
-  // may want to call BeginExclusiveMode after this when you are ready.
-  sql::InitStatus Init(const base::FilePath& history_name);
-
-  // Computes and records various metrics for the database. Should only be
-  // called once and only upon successful Init.
-  void ComputeDatabaseMetrics(const base::FilePath& filename);
-
-  // Call to set the mode on the database to exclusive. The default locking mode
-  // is "normal" but we want to run in exclusive mode for slightly better
-  // performance since we know nobody else is using the database. This is
-  // separate from Init() since the in-memory database attaches to slurp the
-  // data out, and this can't happen in exclusive mode.
-  void BeginExclusiveMode();
-
-  // Returns the current version that we will generate history databases with.
-  static int GetCurrentVersion();
-
-  // Transactions on the history database. Use the Transaction object above
-  // for most work instead of these directly. We support nested transactions
-  // and only commit when the outermost transaction is committed. This means
-  // that it is impossible to rollback a specific transaction. We could roll
-  // back the outermost transaction if any inner one is rolled back, but it
-  // turns out we don't really need this type of integrity for the history
-  // database, so we just don't support it.
-  void BeginTransaction();
-  void CommitTransaction();
-  int transaction_nesting() const {  // for debugging and assertion purposes
-    return db_.transaction_nesting();
-  }
-  void RollbackTransaction();
-
-  // Drops all tables except the URL, and download tables, and recreates them
-  // from scratch. This is done to rapidly clean up stuff when deleting all
-  // history. It is faster and less likely to have problems that deleting all
-  // rows in the tables.
-  //
-  // We don't delete the downloads table, since there may be in progress
-  // downloads. We handle the download history clean up separately in:
-  // content::DownloadManager::RemoveDownloadsFromHistoryBetween.
-  //
-  // Returns true on success. On failure, the caller should assume that the
-  // database is invalid. There could have been an error recreating a table.
-  // This should be treated the same as an init failure, and the database
-  // should not be used any more.
-  //
-  // This will also recreate the supplementary URL indices, since these
-  // indices won't be created automatically when using the temporary URL
-  // table (what the caller does right before calling this).
-  bool RecreateAllTablesButURL();
-
-  // Vacuums the database. This will cause sqlite to defragment and collect
-  // unused space in the file. It can be VERY SLOW.
-  void Vacuum();
-
-  // Try to trim the cache memory used by the database.  If |aggressively| is
-  // true try to trim all unused cache, otherwise trim by half.
-  void TrimMemory(bool aggressively);
-
-  // Razes the database. Returns true if successful.
-  bool Raze();
-
-  // Visit table functions ----------------------------------------------------
-
-  // Update the segment id of a visit. Return true on success.
-  bool SetSegmentID(VisitID visit_id, SegmentID segment_id);
-
-  // Query the segment ID for the provided visit. Return 0 on failure or if the
-  // visit id wasn't found.
-  SegmentID GetSegmentID(VisitID visit_id);
-
-  // Retrieves/Updates early expiration threshold, which specifies the earliest
-  // known point in history that may possibly to contain visits suitable for
-  // early expiration (AUTO_SUBFRAMES).
-  virtual base::Time GetEarlyExpirationThreshold();
-  virtual void UpdateEarlyExpirationThreshold(base::Time threshold);
-
- private:
-#if defined(OS_ANDROID)
-  // AndroidProviderBackend uses the |db_|.
-  friend class AndroidProviderBackend;
-  FRIEND_TEST_ALL_PREFIXES(AndroidURLsMigrationTest, MigrateToVersion22);
-#endif
-  friend class ::HistoryQuickProviderTest;
-  friend class InMemoryURLIndexTest;
-
-  // Overridden from URLDatabase:
-  sql::Connection& GetDB() override;
-
-  // Migration -----------------------------------------------------------------
-
-  // Makes sure the version is up-to-date, updating if necessary. If the
-  // database is too old to migrate, the user will be notified. Returns
-  // sql::INIT_OK iff  the DB is up-to-date and ready for use.
-  //
-  // This assumes it is called from the init function inside a transaction. It
-  // may commit the transaction and start a new one if migration requires it.
-  sql::InitStatus EnsureCurrentVersion();
-
-#if !defined(OS_WIN)
-  // Converts the time epoch in the database from being 1970-based to being
-  // 1601-based which corresponds to the change in Time.internal_value_.
-  void MigrateTimeEpoch();
-#endif
-
-  // ---------------------------------------------------------------------------
-
-  sql::Connection::ErrorCallback error_callback_;
-  sql::Connection db_;
-  sql::MetaTable meta_table_;
-
-  base::Time cached_early_expiration_threshold_;
-
-  DISALLOW_COPY_AND_ASSIGN(HistoryDatabase);
-};
-
-}  // namespace history
-
-#endif  // CHROME_BROWSER_HISTORY_HISTORY_DATABASE_H_