[Sync] Add support for loading, updating and querying delete journals in

sync/syncable/directory_backing_store.h

Index: sync/syncable/directory_backing_store.h
diff --git a/sync/syncable/directory_backing_store.h b/sync/syncable/directory_backing_store.h
index a3e17d87c10cc0633b820615f74e285503d97ecd..7b1a35bcca98465c2f056937863eab883c8fdc69 100644
--- a/sync/syncable/directory_backing_store.h
+++ b/sync/syncable/directory_backing_store.h
@@ -25,6 +25,7 @@ namespace syncable {
 
 struct ColumnSpec;
 typedef Directory::MetahandlesIndex MetahandlesIndex;
+typedef Directory::IdsIndex IdsIndex;
 
 // Interface that provides persistence for a syncable::Directory object. You can
 // load all the persisted data to prime a syncable::Directory on startup by
@@ -56,6 +57,7 @@ class DirectoryBackingStore : public base::NonThreadSafe {
   // NOTE: On success (return value of OPENED), the buckets are populated with
   // newly allocated items, meaning ownership is bestowed upon the caller.
   virtual DirOpenResult Load(MetahandlesIndex* entry_bucket,
+                             IdsIndex* delete_journals,
                              Directory::KernelLoadInfo* kernel_load_info) = 0;
 
   // Updates the on-disk store with the input |snapshot| as a database
@@ -79,7 +81,8 @@ class DirectoryBackingStore : public base::NonThreadSafe {
   bool CreateShareInfoTable(bool is_temporary);
 
   bool CreateShareInfoTableVersion71(bool is_temporary);
-  // Create 'metas' or 'temp_metas' depending on value of is_temporary.
+  // Create 'metas' or 'temp_metas' depending on value of is_temporary. Also
+  // create a 'deleted_metas' table using same schema.
   bool CreateMetasTable(bool is_temporary);
   bool CreateModelsTable();
   bool CreateV71ModelsTable();
@@ -92,10 +95,12 @@ class DirectoryBackingStore : public base::NonThreadSafe {
 
   // Load helpers for entries and attributes.
   bool LoadEntries(MetahandlesIndex* entry_bucket);
+  bool LoadDeleteJournals(IdsIndex* delete_journals);
   bool LoadInfo(Directory::KernelLoadInfo* info);
 
   // Save/update helpers for entries.  Return false if sqlite commit fails.
-  bool SaveEntryToDB(const EntryKernel& entry);
+  static bool SaveEntryToDB(sql::Statement* save_statement,
+                            const EntryKernel& entry);
   bool SaveNewEntryToDB(const EntryKernel& entry);
   bool UpdateEntryToDB(const EntryKernel& entry);
 
@@ -105,9 +110,10 @@ class DirectoryBackingStore : public base::NonThreadSafe {
   // Close save_dbhandle_.  Broken out for testing.
   void EndSave();
 
-  // Removes each entry whose metahandle is in |handles| from the database.
+  // Removes each entry whose metahandle is in |handles| from metas table if
+  // |meta_delete| is true, or from delete journals table if it's false.
   // Does synchronous I/O.  Returns false on error.
-  bool DeleteEntries(const MetahandleSet& handles);
+  bool DeleteEntries(bool meta_delete, const MetahandleSet& handles);
 
   // Drop all tables in preparation for reinitialization.
   void DropAllTables();
@@ -158,15 +164,26 @@ class DirectoryBackingStore : public base::NonThreadSafe {
   bool MigrateVersion80To81();
   bool MigrateVersion81To82();
   bool MigrateVersion82To83();
+  bool MigrateVersion83To84();
 
   scoped_ptr<sql::Connection> db_;
-  sql::Statement save_entry_statement_;
+  sql::Statement save_meta_statment_;
+  sql::Statement save_delete_journal_statment_;
   std::string dir_name_;
 
   // Set to true if migration left some old columns around that need to be
   // discarded.
   bool needs_column_refresh_;
 
+ private:
+  // Helper function for loading entries from specified table.
+  template<class T>
+  bool LoadEntriesInternal(const std::string& table, T* bucket);
+
+  // Prepares |save_statement| for saving entries in |table|.
+  void PrepareSaveEntryStatement(const std::string& table,
+                                 sql::Statement* save_statement);
+
   DISALLOW_COPY_AND_ASSIGN(DirectoryBackingStore);
 };