explain_analyze.txt

Nested Loop  (cost=689.72..799.51 rows=1 width=156) (actual time=150.800..17594.254 rows=173 loops=1)
  ->  Nested Loop  (cost=689.69..797.47 rows=1 width=160) (actual time=150.762..17591.724 rows=173 loops=1)
        Join Filter: (quiz_report_questions.question_id = quiz_user_answer_results.question_id)
        ->  Nested Loop  (cost=0.17..101.94 rows=1 width=150) (actual time=0.109..3.718 rows=173 loops=1)
              ->  Nested Loop  (cost=0.09..29.95 rows=8 width=13) (actual time=0.059..0.964 rows=180 loops=1)
                    ->  Seq Scan on quiz_exercise_lists  (cost=0.00..2.56 rows=5 width=8) (actual time=0.011..0.053 rows=5 loops=1)
                          Filter: (quiz_id = 1)
                          Rows Removed by Filter: 180
                    ->  Index Scan using index_quiz_user_answers_on_user_id_and_quiz_exercise_list_id on quiz_user_answers  (cost=0.09..5.47 rows=2 width=13) (actual time=0.025..0.134 rows=36 loops=5)
                          Index Cond: ((user_id = 1) AND (quiz_exercise_list_id = quiz_exercise_lists.id))
              ->  Index Scan using index_quiz_report_questions_on_question_id on quiz_report_questions  (cost=0.08..9.00 rows=1 width=137) (actual time=0.010..0.012 rows=1 loops=180)
                    Index Cond: (question_id = quiz_user_answers.question_id)
                    Filter: (quiz_id = 1)
                    Rows Removed by Filter: 1
        ->  Bitmap Heap Scan on quiz_user_answer_results  (cost=689.52..695.53 rows=1 width=26) (actual time=101.637..101.657 rows=1 loops=173)
              Recheck Cond: ((user_id = 1) AND (question_id = quiz_user_answers.question_id))
              Filter: (quiz_id = 1)
              Rows Removed by Filter: 15
              ->  BitmapAnd  (cost=689.52..689.52 rows=3 width=0) (actual time=101.621..101.621 rows=0 loops=173)
                    ->  Bitmap Index Scan on index_quiz_user_answer_results_on_user_id  (cost=0.00..56.41 rows=4200 width=0) (actual time=0.286..0.286 rows=2880 loops=173)
                          Index Cond: (user_id = 1)
                    ->  Bitmap Index Scan on index_quiz_user_answer_results_on_question_id  (cost=0.00..633.05 rows=53019 width=0) (actual time=100.712..100.712 rows=199294 loops=173)
                          Index Cond: (question_id = quiz_user_answers.question_id)
  ->  Index Only Scan using quizzes_pkey on quizzes  (cost=0.03..2.03 rows=1 width=4) (actual time=0.008..0.009 rows=1 loops=173)
        Index Cond: (id = 1)
        Heap Fetches: 0

query_expandida.sql

SELECT 
	quiz_user_answer_results.*, 
	quiz_user_answers.answer_review, 
	quiz_report_questions.discipline_plain, 
	quiz_report_questions.answer_correct_count, 
	quiz_report_questions.topic_name, 
	quiz_report_questions.discipline_and_topic_scopes 
FROM 
	"quiz_user_answer_results" 
INNER JOIN 
	"quiz_report_questions" 
	ON 
	"quiz_report_questions"."question_id" = "quiz_user_answer_results"."question_id" 
	AND 
	quiz_report_questions.quiz_id = quiz_user_answer_results.quiz_id 
INNER JOIN 
	"quizzes" 
	ON 
	"quizzes"."id" = "quiz_user_answer_results"."quiz_id" 
INNER JOIN 
	"quiz_exercise_lists" 
	ON 
	"quiz_exercise_lists"."quiz_id" = "quizzes"."id" 
INNER JOIN 
	"quiz_user_answers" 
	ON 
	"quiz_user_answers"."quiz_exercise_list_id" = "quiz_exercise_lists"."id" 
	AND 
	quiz_user_answers.question_id = quiz_user_answer_results.question_id 
	AND 
	quiz_user_answers.user_id = quiz_user_answer_results.user_id 
WHERE 
	"quiz_user_answer_results"."user_id" = ? 
	AND 
	"quiz_user_answer_results"."quiz_id" = ?

quiz_user_answer_result.rb

  def self.answers(quiz_user_progress)
    select([
      'quiz_user_answer_results.*',
      'quiz_user_answers.answer_review',
      'quiz_report_questions.discipline_plain',
      'quiz_report_questions.answer_correct_count',
      'quiz_report_questions.topic_name',
      'quiz_report_questions.discipline_and_topic_scopes'
    ]).joins(:quiz_report_question, :quiz_user_answers)
      .where(
        user_id:                       quiz_user_progress.user_id,
        quiz_user_answer_results:      { quiz_id: quiz_user_progress.quiz_id }
      )
  end