Histogram versions and extended error codes for SQLite databases.

sql/connection.h

 // Copyright (c) 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.
 
 #ifndef SQL_CONNECTION_H_
 #define SQL_CONNECTION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 128 matching lines @@
   void set_exclusive_locking() { exclusive_locking_ = true; }
 
   // Sets the object that will handle errors. Recomended that it should be set
   // before calling Open(). If not set, the default is to ignore errors on
   // release and assert on debug builds.
   // Takes ownership of |delegate|.
   void set_error_delegate(ErrorDelegate* delegate) {
     error_delegate_.reset(delegate);
   }
 
-  // SQLite error codes for errors on all connections are logged to
-  // enum histogram "Sqlite.Error".  Setting this additionally logs
-  // errors to the histogram |name|.
-  void set_error_histogram_name(const std::string& name) {
-    error_histogram_name_ = name;
+  // Set this tag to enable additional connection-type histogramming
+  // for SQLite error codes and database version numbers.
+  void set_histogram_tag(const std::string& tag) {
+    histogram_tag_ = tag;
   }
 
+  // Record a sparse UMA histogram sample under
+  // |name|+"."+|histogram_tag_|.  If |histogram_tag_| is empty, no
+  // histogram is recorded.
+  void AddTaggedHistogram(const std::string& name, size_t sample) const;
+
   // Initialization ------------------------------------------------------------
 
   // Initializes the SQL connection for the given file, returning true if the
   // file could be opened. You can call this or OpenInMemory.
   bool Open(const base::FilePath& path) WARN_UNUSED_RESULT;
 
   // Initializes the SQL connection for a temporary in-memory database. There
   // will be no associated file on disk, and the initial database will be
   // empty. You can call this or Open.
   bool OpenInMemory() WARN_UNUSED_RESULT;
@@ skipping 324 matching lines @@
   // |true| if the connection was closed using RazeAndClose().  Used
   // to enable diagnostics to distinguish calls to never-opened
   // databases (incorrect use of the API) from calls to once-valid
   // databases.
   bool poisoned_;
 
   // This object handles errors resulting from all forms of executing sqlite
   // commands or statements. It can be null which means default handling.
   scoped_ptr<ErrorDelegate> error_delegate_;
 
-  // Auxiliary error-code histogram.
-  std::string error_histogram_name_;
+  // Tag for auxiliary histograms.
+  std::string histogram_tag_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };
 
 }  // namespace sql
 
 #endif  // SQL_CONNECTION_H_