gistfile1.txt

mysql> explain SELECT articles.id, articles.author_id, articles.primary_image_id, articles.hit_count, articles.blurb, articles.teaser, articles.title, articles.permalink, articles.created_at, articles.comments_count FROM articles WHERE articles.deleted_at IS NULL AND articles.created_at > '2008-10-26 00:00:00' AND articles.id IN (SELECT taggable_id FROM taggings WHERE tag_id = 16 AND taggable_type = 'Article') ORDER BY articles.id DESC LIMIT 5 \G
*************************** 1. row ***************************
           id: 1
  select_type: PRIMARY
        table: articles
         type: ref
possible_keys: idx_articles_on_created_at_id,idx_deleted_at_admin_edited_regular_edited_trusted_edited_score,idx_deleted_at_score,index_articles_on_deleted_at
          key: idx_deleted_at_admin_edited_regular_edited_trusted_edited_score
      key_len: 9
          ref: const
         rows: 45335
        Extra: Using where; Using filesort
*************************** 2. row ***************************
           id: 2
  select_type: DEPENDENT SUBQUERY
        table: taggings
         type: index_subquery
possible_keys: index_taggings_on_taggable_id,index_taggings_i1,index_taggings_on_tag_id_and_taggable_type,i2
          key: index_taggings_i1
      key_len: 775
          ref: func,const,const
         rows: 1
        Extra: Using index; Using where
2 rows in set (0.01 sec)

mysql>