mysql - Rails 2.3 paginate_by_sqlクエリが遅い

Question

query の最後にLEFT JOIN多数の複雑な SQL を持つ paginate_by_sql を最適化するにはどうすればよいですか?GROUP BY

以外のオプションはありpaginate_by_sqlますか?

私たちのプロジェクトでは、Rails 2.3 と Ruby 1.8 と MySQL を使用しています。

     SELECT Table.name as sql_course_name,Table.id as sql_course_id, 
            table1.name as sql_subject_name, table1.id as sql_subject_id, 
            table3.id as sql_s_c_id, table5.*
       FROM table5
  LEFT JOIN table2 on table2.deleted = false and table2.content_id = table5.id
  LEFT JOIN lessons on lessons.deleted = false and lessons.id = table2.lesson_id
  LEFT JOIN table3 on table3.deleted = false and table3.content_id = table5.id 
  LEFT JOIN table1 on table1.deleted = false and table1.id = table3.subject_id 
  LEFT JOIN Table on Table.deleted = false and table1.course_id = Table.id
  LEFT JOIN table4 on table4.deleted = false and table4.content_id = table5.id
  LEFT JOIN attachments on attachments.deleted = false and attachments.id = table4.attachment_id
      WHERE #{str} 
   GROUP BY table5.id, table3.id