predictors: Remove unused field from the resource_prefetch_predictor database.

chrome/browser/predictors/resource_prefetch_predictor_tables.h

 // Copyright 2014 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 CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TABLES_H_
 #define CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TABLES_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 26 matching lines @@
 //  - UrlMetadataTable - misc data for Urls (like last visit time).
 //  - HostResourceTable - resources per host.
 //  - HostMetadataTable - misc data for hosts.
 class ResourcePrefetchPredictorTables : public PredictorTableBase {
  public:
   // Used in the UrlResourceTable and HostResourceTable to store resources
   // required for the page or host.
   struct ResourceRow {
     ResourceRow();
     ResourceRow(const ResourceRow& other);
-    ResourceRow(const std::string& main_frame_url,
-                const std::string& resource_url,
+    ResourceRow(const std::string& resource_url,
                 content::ResourceType resource_type,
                 int number_of_hits,
                 int number_of_misses,
                 int consecutive_misses,
                 double average_position,
                 net::RequestPriority priority,
                 bool has_validators,
                 bool always_revalidate);
     void UpdateScore();
     bool operator==(const ResourceRow& rhs) const;
     static void FromProto(const ResourceData& proto, ResourceRow* row);
     void ToProto(ResourceData* resource_data) const;
 
-    // Stores the host for host based data, main frame Url for the Url based
-    // data. This field is cleared for efficiency reasons and the code outside
-    // this class should not assume it is set.
-    std::string primary_key;
-
     GURL resource_url;
     content::ResourceType resource_type;
     size_t number_of_hits;

[pasko, 2016/08/26 13:40:30]

Do we want to still plumb these one by one in FromProto/ToProto? Is removing
them a plan for the next cleanup?

[Benoit L, 2016/08/29 13:11:39]

If the proto doesn't reflect everything and needs methods added, no.

     size_t number_of_misses;
     size_t consecutive_misses;
     double average_position;
     net::RequestPriority priority;
     bool has_validators;
     bool always_revalidate;
 
     // Not stored.
     float score;
   };
@@ skipping 39 matching lines @@
                   const std::vector<std::string>& hosts);
 
   // Wrapper over DeleteData for convenience.
   virtual void DeleteSingleDataPoint(const std::string& key,
                                      PrefetchKeyType key_type);
 
   // Deletes all data in all the tables.
   virtual void DeleteAllData();
 
   // The maximum length of the string that can be stored in the DB.
-  static const size_t kMaxStringLength;
+  static const size_t kMaxStringLength = 1024;

[pasko, 2016/08/26 13:40:30]

I would recommend constexpr. The idea of including this constant in all the
various .cc files and then resolving the duplicates in the linker is not
uncommon in C++ land, but somehow feels less optimal, given a strictly better
alternative. 

[Benoit L, 2016/08/29 13:11:39]

Done.

 
  private:
   friend class PredictorDatabaseInternal;
   friend class MockResourcePrefetchPredictorTables;
 
   ResourcePrefetchPredictorTables();
   ~ResourcePrefetchPredictorTables() override;
 
   // Helper functions below help perform functions on the Url and host table
   // using the same code.
   void GetAllDataHelper(PrefetchKeyType key_type,
                         PrefetchDataMap* data_map,
                         std::vector<std::string>* to_delete);
   bool UpdateDataHelper(const PrefetchData& data);
   void DeleteDataHelper(PrefetchKeyType key_type,
                         const std::vector<std::string>& keys);
 
   // Returns true if the strings in the |data| are less than |kMaxStringLength|
   // in length.
-  bool StringsAreSmallerThanDBLimit(const PrefetchData& data) const;
+  static bool StringsAreSmallerThanDBLimit(const PrefetchData& data);
 
   // PredictorTableBase methods.
   void CreateTableIfNonExistent() override;
   void LogDatabaseStats() override;
 
   static bool DropTablesIfOutdated(sql::Connection* db);
 
   // Helpers to return Statements for cached Statements. The caller must take
   // ownership of the return Statements.
   sql::Statement* GetUrlResourceDeleteStatement();
   sql::Statement* GetUrlResourceUpdateStatement();
   sql::Statement* GetUrlMetadataDeleteStatement();
   sql::Statement* GetUrlMetadataUpdateStatement();
 
   sql::Statement* GetHostResourceDeleteStatement();
   sql::Statement* GetHostResourceUpdateStatement();
   sql::Statement* GetHostMetadataDeleteStatement();
   sql::Statement* GetHostMetadataUpdateStatement();
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePrefetchPredictorTables);
 };
 
 }  // namespace predictors
 
 #endif  // CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TABLES_H_