[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..1d5a0870f409d79d76ca3fb7e026d35a118186e3 100644
--- a/components/history/core/browser/thumbnail_database.cc
+++ b/components/history/core/browser/thumbnail_database.cc
@@ -412,6 +412,32 @@ 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(
+      SQL_FROM_HERE,
+      "SELECT favicons.id, favicons.url, icon_mapping.page_url FROM "
+      "favicons, favicon_bitmaps, icon_mapping WHERE favicon_bitmaps.icon_id = "

[brettw, 2017/07/11 19:26:43]

Can you express this as an explicit JOIN across the tables rather than
implicitly with WHERE? Then you can reserve the WHERE clause for the thing
you're actually looking for.

[jkrcal, 2017/07/13 20:26:10]

Done.

+      "icon_mapping.icon_id AND favicons.id = favicon_bitmaps.icon_id AND "
+      "((last_requested=0 AND last_updated=0) OR "

[brettw, 2017/07/11 19:26:43]

I like to be explicit about the table names for the columns being selected when
doing a query across multiple tables.

[jkrcal, 2017/07/13 20:26:10]

Done.

+      "(last_requested>0 AND 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 +804,14 @@ bool ThumbnailDatabase::DeleteIconMappings(const GURL& page_url) {
   return statement.Run();
 }
 
+bool ThumbnailDatabase::DeleteIconMappingsForFaviconId(
+    favicon_base::FaviconID id) {
+  sql::Statement statement(db_.GetCachedStatement(
+      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=?"));