hide pages from crawler for degenerate queries

app/logical/post_sets/post.rb

@@ -140,6 +140,19 @@ module PostSets
       post_count == Danbooru.config.blank_tag_search_fast_count
     end
 
+    def hide_from_crawler?
+      return true if !is_single_tag?
+      return true if is_pattern_search?
+      return true if params[:page].to_i > 1
+      return true if is_metatag_search?
+      false
+    end
+
+    def is_metatag_search?
+      # filter out some common metatags
+      tag_string =~ /(?:rating|user|fav|status|order|source|score|width|height):/
+    end
+
     def is_single_tag?
       tag_array.size == 1
     end