Sync: Avoid 3 passes over SyncDarta DB when loading the directory from the disk

sync/syncable/directory_backing_store.cc

 // Copyright 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.
 
 #include "sync/syncable/directory_backing_store.h"
 
 #include "build/build_config.h"
 
 #include <limits>
 
@@ skipping 520 matching lines @@
     return false;
 
   SafeDropTable("share_info");
   if (!db_->Execute("ALTER TABLE temp_share_info RENAME TO share_info"))
     return false;
 
   needs_column_refresh_ = false;
   return true;
 }
 
-bool DirectoryBackingStore::LoadEntries(
-    Directory::MetahandlesMap* handles_map) {
+bool DirectoryBackingStore::LoadEntries(Directory::MetahandlesMap* handles_map,
+                                        MetahandleSet* metahandles_to_purge) {
   string select;
   select.reserve(kUpdateStatementBufferSize);
   select.append("SELECT ");
   AppendColumnList(&select);
   select.append(" FROM metas");
 
   sql::Statement s(db_->GetUniqueStatement(select.c_str()));
 
   while (s.Step()) {
     scoped_ptr<EntryKernel> kernel = UnpackEntry(&s);
     // A null kernel is evidence of external data corruption.
     if (!kernel)
       return false;
 
     int64 handle = kernel->ref(META_HANDLE);
-    (*handles_map)[handle] = kernel.release();
+    if (SafeToPurgeOnLoading(*kernel))
+      metahandles_to_purge->insert(handle);
+    else
+      (*handles_map)[handle] = kernel.release();
   }
   return s.Succeeded();
 }
 
+bool DirectoryBackingStore::SafeToPurgeOnLoading(
+    const EntryKernel& entry) const {
+  if (entry.ref(IS_DEL)) {
+    if (!entry.ref(IS_UNSYNCED) && !entry.ref(IS_UNAPPLIED_UPDATE))
+      return true;
+    else if (!entry.ref(ID).ServerKnows())
+      return true;
+  }
+  return false;
+}
+
 bool DirectoryBackingStore::LoadDeleteJournals(
     JournalIndex* delete_journals) {
   string select;
   select.reserve(kUpdateStatementBufferSize);
   select.append("SELECT ");
   AppendColumnList(&select);
   select.append(" FROM deleted_metas");
 
   sql::Statement s(db_->GetUniqueStatement(select.c_str()));
 
@@ skipping 63 matching lines @@
 }
 
 /* static */
 bool DirectoryBackingStore::SaveEntryToDB(sql::Statement* save_statement,
                                           const EntryKernel& entry) {
   save_statement->Reset(true);
   BindFields(entry, save_statement);
   return save_statement->Run();
 }
 
-bool DirectoryBackingStore::DropDeletedEntries() {
-  if (!db_->Execute("DELETE FROM metas "
-                    "WHERE is_del > 0 "
-                    "AND is_unsynced < 1 "
-                    "AND is_unapplied_update < 1")) {
-    return false;
-  }
-  if (!db_->Execute("DELETE FROM metas "
-                    "WHERE is_del > 0 "
-                    "AND id LIKE 'c%'")) {
-    return false;
-  }
-  return true;
-}
-
 bool DirectoryBackingStore::SafeDropTable(const char* table_name) {
   string query = "DROP TABLE IF EXISTS ";
   query.append(table_name);
   return db_->Execute(query.c_str());
 }
 
 void DirectoryBackingStore::DropAllTables() {
   SafeDropTable("metas");
   SafeDropTable("temp_metas");
   SafeDropTable("share_info");
@@ skipping 917 matching lines @@
   }
   query.append(" ) ");
   values.append(" )");
   query.append(values);
   save_statement->Assign(db_->GetUniqueStatement(
       base::StringPrintf(query.c_str(), "metas").c_str()));
 }
 
 }  // namespace syncable
 }  // namespace syncer