[Thumbnails DB] Add functionality to clear unused on-demand favicons.

components/history/core/browser/thumbnail_database.cc

Index: components/history/core/browser/thumbnail_database.cc
diff --git a/components/history/core/browser/thumbnail_database.cc b/components/history/core/browser/thumbnail_database.cc
index c8b430f4f71d8dd70f0111995c5ce74297cec7d9..8a7290182b783c4f110b40fdfc86a42d553529e2 100644
--- a/components/history/core/browser/thumbnail_database.cc
+++ b/components/history/core/browser/thumbnail_database.cc
@@ -412,6 +412,33 @@ void ThumbnailDatabase::TrimMemory(bool aggressively) {
   db_.TrimMemory(aggressively);
 }
 
+std::map<favicon_base::FaviconID, IconMappingsForExpiry>
+ThumbnailDatabase::GetOldOnDemandFavicons(base::Time threshold) {
+  // Restrict to on-demand bitmaps (i.e. with last_requested != 0).
+  // TODO(jkrcal): In M63, remove the "(last_requested=0 AND last_updated=0)"
+  // clause which is only transitional - to clean up expired icons (previously,
+  // on-demand favicons were stored as expired on-visit favicons).
+  sql::Statement old_icons(db_.GetCachedStatement(

[brettw, 2017/07/13 23:50:17]

Can you make this be a non-cached ("unique") statement? Since we execute it so
rarely, the caching will just waste memory.

[mastiz, 2017/07/18 07:48:19]

Done.

+      SQL_FROM_HERE,
+      "SELECT favicons.id, favicons.url, icon_mapping.page_url FROM "

[brettw, 2017/07/13 23:50:16]

Can you wrap this SQL string like code so it's readable?

      "SELECT favicons.id, favicons.url, icon_mapping.page_url "
      "FROM favicons "
      "JOIN favicon_bitmaps ON (favicon_bitmaps.icon_id = favicons.id) "
      "JOIN icon_mapping ON (icon_mapping.icon_id = favicon_bitmaps.icon_id) "
      "WHERE ((favicon_bitmaps.last_requested = 0 AND "
              "favicon_bitmaps.last_updated = 0) OR "
             "(favicon_bitmaps.last_requested > 0 AND "
              "favicon_bitmaps.last_requested < ?))"

[mastiz, 2017/07/18 07:48:19]

Done, with slight modifications because indentation needs to be inside the
string literal.

+      "favicons JOIN favicon_bitmaps ON (favicon_bitmaps.icon_id = "
+      "favicons.id) JOIN icon_mapping ON (icon_mapping.icon_id = "
+      "favicon_bitmaps.icon_id) WHERE ((favicon_bitmaps.last_requested=0 AND "
+      "favicon_bitmaps.last_updated=0) OR (favicon_bitmaps.last_requested>0 "
+      "AND favicon_bitmaps.last_requested<?));"));
+  old_icons.BindInt64(0, threshold.ToInternalValue());
+
+  std::map<favicon_base::FaviconID, IconMappingsForExpiry> icon_mappings;
+
+  while (old_icons.Step()) {
+    favicon_base::FaviconID id = old_icons.ColumnInt64(0);
+    icon_mappings[id].icon_url = GURL(old_icons.ColumnString(1));
+    icon_mappings[id].page_urls.push_back(GURL(old_icons.ColumnString(2)));
+  }
+
+  return icon_mappings;
+}
+
 bool ThumbnailDatabase::GetFaviconBitmapIDSizes(
     favicon_base::FaviconID icon_id,
     std::vector<FaviconBitmapIDSize>* bitmap_id_sizes) {
@@ -778,6 +805,14 @@ bool ThumbnailDatabase::DeleteIconMappings(const GURL& page_url) {
   return statement.Run();
 }
 
+bool ThumbnailDatabase::DeleteIconMappingsForFaviconId(
+    favicon_base::FaviconID id) {
+  sql::Statement statement(db_.GetCachedStatement(

[brettw, 2017/07/13 23:50:17]

Maybe do a unique statement here too. Might be worth adding a comment about how
this is called rarely so it's not cached.

[mastiz, 2017/07/18 07:48:19]

Done.

+      SQL_FROM_HERE, "DELETE FROM icon_mapping WHERE icon_id=?"));
+  statement.BindInt64(0, id);
+  return statement.Run();
+}
+
 bool ThumbnailDatabase::DeleteIconMapping(IconMappingID mapping_id) {
   sql::Statement statement(db_.GetCachedStatement(SQL_FROM_HERE,
       "DELETE FROM icon_mapping WHERE id=?"));