Revert CL 117933003. Re-add resource speculative prefetching code.

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 <map>
+#include <string>
+#include <vector>
+
+#include "base/time/time.h"
+#include "chrome/browser/predictors/predictor_table_base.h"
+#include "chrome/browser/predictors/resource_prefetch_common.h"
+#include "content/public/common/resource_type.h"
+#include "url/gurl.h"
+
+namespace sql {
+class Statement;
+}
+
+namespace predictors {
+
+// Interface for database tables used by the ResourcePrefetchPredictor.
+// All methods except the constructor and destructor need to be called on the DB
+// thread.
+//
+// Currently manages:
+//  - UrlResourceTable - resources per Urls.
+//  - 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,
+                content::ResourceType resource_type,
+                int number_of_hits,
+                int number_of_misses,
+                int consecutive_misses,
+                double average_position);
+    void UpdateScore();
+    bool operator==(const ResourceRow& rhs) 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;
+    size_t number_of_misses;
+    size_t consecutive_misses;
+    double average_position;
+
+    // Not stored.
+    float score;
+  };
+  typedef std::vector<ResourceRow> ResourceRows;
+
+  // Sorts the ResourceRows by score, descending.
+  struct ResourceRowSorter {
+    bool operator()(const ResourceRow& x, const ResourceRow& y) const;
+  };
+
+  // Aggregated data for a Url or Host. Although the data differs slightly, we
+  // store them in the same structure, because most of the fields are common and
+  // it allows us to use the same functions.
+  struct PrefetchData {
+    PrefetchData(PrefetchKeyType key_type, const std::string& primary_key);
+    PrefetchData(const PrefetchData& other);
+    ~PrefetchData();
+    bool operator==(const PrefetchData& rhs) const;
+
+    bool is_host() const { return key_type == PREFETCH_KEY_TYPE_HOST; }
+
+    // Is the data a host as opposed to a Url?
+    PrefetchKeyType key_type;  // Not const to be able to assign.
+    std::string primary_key;  // is_host() ? main frame url : host.
+
+    base::Time last_visit;
+    ResourceRows resources;
+  };
+  // Map from primary key to PrefetchData for the key.
+  typedef std::map<std::string, PrefetchData> PrefetchDataMap;
+
+  // Returns data for all Urls and Hosts.
+  virtual void GetAllData(PrefetchDataMap* url_data_map,
+                          PrefetchDataMap* host_data_map);
+
+  // Updates data for a Url and a host. If either of the |url_data| or
+  // |host_data| has an empty primary key, it will be ignored.
+  // Note that the Urls and primary key in |url_data| and |host_data| should be
+  // less than |kMaxStringLength| in length.
+  virtual void UpdateData(const PrefetchData& url_data,
+                          const PrefetchData& host_data);
+
+  // Delete data for the input |urls| and |hosts|.
+  virtual void DeleteData(const std::vector<std::string>& urls,
+                  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;
+
+ private:
+  friend class PredictorDatabaseInternal;
+  friend class MockResourcePrefetchPredictorTables;
+
+  ResourcePrefetchPredictorTables();
+  virtual ~ResourcePrefetchPredictorTables();
+
+  // 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;
+
+  // PredictorTableBase methods.
+  virtual void CreateTableIfNonExistent() OVERRIDE;
+  virtual void LogDatabaseStats() OVERRIDE;
+
+  // 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_