sql/diagnostic_error_delegate.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SQL_DIAGNOSTIC_ERROR_DELEGATE_H_
   6 #define SQL_DIAGNOSTIC_ERROR_DELEGATE_H_
   7 #pragma once
   8
   9 #include "base/logging.h"
  10 #include "base/metrics/histogram.h"
  11 #include "sql/connection.h"
  12
  13 namespace sql {
  14
  15 // This class handles the exceptional sqlite errors that we might encounter
  16 // if for example the db is corrupted. Right now we just generate a UMA
  17 // histogram for release and an assert for debug builds.
  18 //
  19 // Why is it a template you ask? well, that is a funny story. The histograms
  20 // need to be singletons that is why they are always static at the function
  21 // scope, but we cannot use the Singleton class because they are not default
  22 // constructible. The template parameter makes the compiler to create unique
  23 // classes that don't share the same static variable.
  24 template <class UniqueT>
  25 class DiagnosticErrorDelegate : public ErrorDelegate {
  26  public:
  27
  28   virtual int OnError(int error, Connection* connection,
  29                       Statement* stmt) {
  30     NOTREACHED() << "sqlite error " << error
  31                  << ", errno " << connection->GetLastErrno()
  32                  << ": " << connection->GetErrorMessage();
  33     RecordErrorInHistogram(error);
  34     return error;
  35   }
  36
  37  private:
  38   static void RecordErrorInHistogram(int error) {
  39     // Trim off the extended error codes.
  40     error &= 0xff;
  41
  42     // The histogram values from sqlite result codes go currently from 1 to
  43     // 26 currently but 50 gives them room to grow.
  44     UMA_HISTOGRAM_ENUMERATION(UniqueT::name(), error, 50);
  45   }
  46 };
  47
  48 }  // namespace sql
  49
  50 #endif  // SQL_DIAGNOSTIC_ERROR_DELEGATE_H_