Cleaning up url_index_private_data and in_memory_url_index_types.

components/omnibox/browser/url_index_private_data.h

Index: components/omnibox/browser/url_index_private_data.h
diff --git a/components/omnibox/browser/url_index_private_data.h b/components/omnibox/browser/url_index_private_data.h
index 50bcf4b7ebc141548414f53a4b833f35de5717db..3b7afd8b2f5dddb1577ddaf1c2f900fbcf54a0b1 100644
--- a/components/omnibox/browser/url_index_private_data.h
+++ b/components/omnibox/browser/url_index_private_data.h
@@ -8,6 +8,7 @@
 #include <stddef.h>
 
 #include <set>
+#include <stack>
 #include <string>
 
 #include "base/files/file_path.h"
@@ -204,9 +205,15 @@ class URLIndexPrivateData
 
   // URL History indexing support functions.
 
-  // Composes a set of history item IDs by intersecting the set for each word
+  // Composes a vector of history item IDs by intersecting the set for each word
   // in |unsorted_words|.
-  HistoryIDSet HistoryIDSetFromWords(const String16Vector& unsorted_words);
+  HistoryIDVector HistoryIDsFromWords(const String16Vector& unsorted_words);
+
+  // Trim the candidate pool if it is large. Note that we do not filter out

[Peter Kasting, 2017/02/18 01:46:31]

Nit: Trims

Might want to give a little idea of how/why, e.g. "Trims the candidate pool in
advance of doing proper substring searching, to cap the cost of such searching. 
Discards the least-relevant items (based on visit stats), which are least likely
to score highly in the end.  To minimize the risk of discarding a valuable URL,
the candidate pool is still left two orders of magnitude larger than the final
number of results returned from the HQP."

[dyaroshev, 2017/02/18 11:48:14]

Done.

+  // items that do not contain the search terms as proper substrings --
+  // doing so is the performance-costly operation we are trying to avoid in
+  // order to maintain omnibox responsiveness.
+  void TrimHistoryIdsPool(HistoryIDVector* history_ids) const;
 
   // Helper function to HistoryIDSetFromWords which composes a set of history
   // ids for the given term given in |term|.
@@ -216,13 +223,12 @@ class URLIndexPrivateData
   WordIDSet WordIDSetForTermChars(const Char16Set& term_chars);
 
   // Helper function for HistoryItemsForTerms().  Fills in |scored_items| from
-  // the matches listed in |history_id_set|.
-  void HistoryIdSetToScoredMatches(
-      HistoryIDSet history_id_set,
-      const base::string16& lower_raw_string,
-      const TemplateURLService* template_url_service,
-      bookmarks::BookmarkModel* bookmark_model,
-      ScoredHistoryMatches* scored_items) const;
+  // the matches listed in |history_ids|.
+  void HistoryIdsToScoredMatches(HistoryIDVector history_ids,
+                                 const base::string16& lower_raw_string,
+                                 const TemplateURLService* template_url_service,
+                                 bookmarks::BookmarkModel* bookmark_model,
+                                 ScoredHistoryMatches* scored_items) const;
 
   // Fills in |terms_to_word_starts_offsets| according to where the word starts
   // in each term.  For example, in the term "-foo" the word starts at offset 1.
@@ -253,17 +259,9 @@ class URLIndexPrivateData
   // history item identified by |history_id| to the index.
   void AddWordToIndex(const base::string16& uni_word, HistoryID history_id);
 
-  // Creates a new entry in the word/history map for |word_id| and add
-  // |history_id| as the initial element of the word's set.
-  void AddWordHistory(const base::string16& uni_word, HistoryID history_id);
-
-  // Updates an existing entry in the word/history index by adding the
-  // |history_id| to set for |word_id| in the word_id_history_map_.
-  void UpdateWordHistory(WordID word_id, HistoryID history_id);
-
-  // Adds |word_id| to |history_id|'s entry in the history/word map,
-  // creating a new entry if one does not already exist.
-  void AddToHistoryIDWordMap(HistoryID history_id, WordID word_id);
+  // Adds a new entry to word_list. Uses previously freed positions if
+  // available.
+  WordID AddNewWordToWordList(const base::string16& term);
 
   // Removes |row| and all associated words and characters from the index.
   void RemoveRowFromIndex(const history::URLRow& row);
@@ -346,7 +344,7 @@ class URLIndexPrivateData
   // modified or deleted old words may be removed from the index, in which
   // case the slots for those words are added to available_words_ for resuse
   // by future URL updates.
-  WordIDSet available_words_;
+  std::stack<WordID> available_words_;
 
   // A one-to-one mapping from the a word string to its slot number (i.e.
   // WordID) in the |word_list_|.