sql/diagnostic_error_delegate.h

   1 // Copyright (c) 2012 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 #include "sql/sql_export.h"
  13
  14 namespace sql {
  15
  16 // This class handles the exceptional sqlite errors that we might encounter
  17 // if for example the db is corrupted. Right now we just generate a UMA
  18 // histogram for release and an assert for debug builds.
  19 //
  20 // Why is it a template you ask? well, that is a funny story. The histograms
  21 // need to be singletons that is why they are always static at the function
  22 // scope, but we cannot use the Singleton class because they are not default
  23 // constructible. The template parameter makes the compiler to create unique
  24 // classes that don't share the same static variable.
  25 template <class UniqueT>
  26 class DiagnosticErrorDelegate : public ErrorDelegate {
  27  public:
  28
  29   virtual int OnError(int error, Connection* connection,
  30                       Statement* stmt) {
  31     LOG(ERROR) << "sqlite error " << error
  32                << ", errno " << connection->GetLastErrno()
  33                << ": " << connection->GetErrorMessage();
  34     RecordErrorInHistogram(error);
  35     return error;
  36   }
  37
  38  private:
  39   static void RecordErrorInHistogram(int error) {
  40     // Trim off the extended error codes.
  41     error &= 0xff;
  42
  43     // The histogram values from sqlite result codes go currently from 1 to
  44     // 26 currently but 50 gives them room to grow.
  45     UMA_HISTOGRAM_ENUMERATION(UniqueT::name(), error, 50);
  46   }
  47 };
  48
  49 }  // namespace sql
  50
  51 #endif  // SQL_DIAGNOSTIC_ERROR_DELEGATE_H_