Compressed activity log database storage

chrome/browser/extensions/activity_log/activity_database.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_DATABASE_H_
 #define CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_DATABASE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 57 matching lines @@
   class Delegate {
    protected:
     friend class ActivityDatabase;
 
     // A Delegate is never directly deleted; it should instead delete itself
     // after any final cleanup when OnDatabaseClose() is invoked.
     virtual ~Delegate() {}
 
     // Initializes the database schema; this gives a policy a chance to create
     // or update database tables as needed.  Should return true on success.
+    // Will be called from within a database transaction.
     virtual bool InitDatabase(sql::Connection* db) = 0;
 
     // Requests that the policy flush any pending actions to the database.
-    // Should return true on success or false on a database error.
+    // Should return true on success or false on a database error.  Will not be
+    // called from a transaction (the implementation may wish to use a
+    // transaction for the flush).
     virtual bool FlushDatabase(sql::Connection* db) = 0;
 
     // Called if the database encounters a permanent error; the policy should
     // not expect to make any future writes to the database and may want to
     // discard any queued data.
     virtual void OnDatabaseFailure() = 0;
 
     // Called by ActivityDatabase just before the ActivityDatabase object is
     // deleted.  The database will make no further callbacks after invoking
     // this method, so it is an appropriate time for the policy to delete
     // itself.
     virtual void OnDatabaseClose() = 0;
   };
 
+  // Value to be passed to AdviseFlush below to force a database flush.
+  static const int kFlushImmediately = -1;
+
   // Need to call Init to actually use the ActivityDatabase.  The Delegate
   // provides hooks for an ActivityLogPolicy to control the database schema and
   // reads/writes.
   explicit ActivityDatabase(Delegate* delegate);
 
   // Opens the DB.  This invokes OnDatabaseInit in the delegate to create or
   // update the database schema if needed.
   void Init(const base::FilePath& db_name);
 
   // An ActivityLogPolicy should call this to kill the ActivityDatabase.
   void Close();
 
   // Inform the database that there may be additional data which could be
-  // written out.
-  // TODO(mvrable): Add a method to force a database flush, or perhaps pass
-  // hints to the database about how much data is queued up so the database can
-  // flush before the timeout if there is a large amount of data?
-  void NotifyAction();
+  // written out.  The size parameter should indicate (approximately) how many
+  // records are queued to be written; the database may use this information to
+  // schedule a flush early if too much data is queueing up.  A value of
+  // kFlushImmediately will force an immediate call into
+  // Delegate::FlushDatabase(); otherwise, it is up to the database to
+  // determine when to flush.
+  void AdviseFlush(int size);
 
   // Turns off batch I/O writing mode. This should only be used in unit tests,
   // browser tests, or in our special --enable-extension-activity-log-testing
   // policy state.
   void SetBatchModeForTesting(bool batch_mode);
 
   bool is_db_valid() const { return valid_db_; }
 
   // A helper method for initializing or upgrading a database table.  The
   // content_fields array should list the names of all of the columns in the
@@ skipping 57 matching lines @@
   sql::Connection db_;
   bool valid_db_;
   bool batch_mode_;
   base::RepeatingTimer<ActivityDatabase> timer_;
   bool already_closed_;
   bool did_init_;
 
   friend class ActivityLogDatabasePolicy;
   FRIEND_TEST_ALL_PREFIXES(ActivityDatabaseTest, BatchModeOff);
   FRIEND_TEST_ALL_PREFIXES(ActivityDatabaseTest, BatchModeOn);
+  FRIEND_TEST_ALL_PREFIXES(ActivityDatabaseTest, BatchModeFlush);
   DISALLOW_COPY_AND_ASSIGN(ActivityDatabase);
 };
 
 }  // namespace extensions
 #endif  // CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_DATABASE_H_