Compressed activity log database storage

chrome/browser/extensions/activity_log/database_string_table.cc

+// Copyright 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 "chrome/browser/extensions/activity_log/database_string_table.h"
+
+#include "base/strings/stringprintf.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+
+using base::StringPrintf;
+
+namespace extensions {
+
+DatabaseStringTable::DatabaseStringTable(const std::string& table)
+    : table_(table) {}
+
+DatabaseStringTable::~DatabaseStringTable() {}
+
+bool DatabaseStringTable::Initialize(sql::Connection* connection) {
+  if (!connection->DoesTableExist(table_.c_str())) {
+    return connection->Execute(StringPrintf(
+        "CREATE TABLE %s (id INTEGER PRIMARY KEY, value TEXT NOT NULL); "
+        "CREATE UNIQUE INDEX %s_index ON %s(value)",
+        table_.c_str(),
+        table_.c_str(),
+        table_.c_str()).c_str());
+  } else {
+    return true;
+  }
+}
+
+bool DatabaseStringTable::StringToInt(sql::Connection* connection,
+                                      const std::string& value,
+                                      int64* id) {
+  std::map<std::string, int64>::const_iterator lookup =
+      value_to_id_.find(value);
+  if (lookup != value_to_id_.end()) {
+    *id = lookup->second;
+    return true;
+  }
+
+  // Operate on the assumption that the cache does a good job on
+  // frequently-used strings--if there is a cache miss, first act on the
+  // assumption that the string is not in the database either.
+  sql::Statement update(connection->GetUniqueStatement(
+      StringPrintf("INSERT OR IGNORE INTO %s(value) VALUES (?)", table_.c_str())
+          .c_str()));
+  update.BindString(0, value);
+  if (!update.Run())
+    return false;
+
+  if (connection->GetLastChangeCount() == 1) {
+    *id = connection->GetLastInsertRowId();
+    id_to_value_[*id] = value;
+    value_to_id_[value] = *id;
+    return true;
+  }
+
+  // The specified string may have already existed in the database, in which
+  // case the insert above will have been ignored.  If this happens, do a
+  // lookup to find the old value.
+  sql::Statement query(connection->GetUniqueStatement(
+      StringPrintf("SELECT id FROM %s WHERE value = ?", table_.c_str())
+          .c_str()));
+  query.BindString(0, value);
+  if (!query.Step())
+    return false;
+  *id = query.ColumnInt64(0);
+  id_to_value_[*id] = value;
+  value_to_id_[value] = *id;
+  return true;
+}
+
+bool DatabaseStringTable::IntToString(sql::Connection* connection,
+                                      int64 id,
+                                      std::string* value) {
+  std::map<int64, std::string>::const_iterator lookup =
+      id_to_value_.find(id);
+  if (lookup != id_to_value_.end()) {
+    *value = lookup->second;
+    return true;
+  }
+
+  sql::Statement query(connection->GetUniqueStatement(
+      StringPrintf("SELECT value FROM %s WHERE id = ?", table_.c_str())
+          .c_str()));
+  query.BindInt64(0, id);
+  if (!query.Step())
+    return false;
+
+  *value = query.ColumnString(0);
+  id_to_value_[id] = *value;
+  value_to_id_[*value] = id;
+  return true;
+}
+
+void DatabaseStringTable::ClearCache() {
+  id_to_value_.clear();
+  value_to_id_.clear();
+}
+
+}  // namespace extensions