GroupAggregate  (cost=2310716.58..2808582.95 rows=9483169 width=80) (actual time=35578.168..42287.700 rows=836894 loops=1)
   ->  Sort  (cost=2310716.58..2334424.50 rows=9483169 width=80) (actual time=35578.157..38973.645 rows=9456652 loops=1)
         Sort Key: iquiza.id, iquiz.id, iquiz.timeclose, iquiz.timelimit
         Sort Method:  external merge  Disk: 462176kB
         ->  Merge Left Join  (cost=558.33..790390.49 rows=9483169 width=80) (actual time=1.106..17029.782 rows=9456652 loops=1)
               Merge Cond: (iquiza.quiz = qgo1.quiz)
               Join Filter: (qgo1.groupid = gm.groupid)
               ->  Merge Left Join  (cost=546.24..765769.76 rows=9483169 width=88) (actual time=1.036..15210.304 rows=9456652 loops=1)
                     Merge Cond: (iquiza.quiz = qgo2.quiz)
                     Join Filter: (qgo2.groupid = gm.groupid)
                     ->  Merge Left Join  (cost=517.48..698123.67 rows=9483169 width=80) (actual time=0.764..12864.522 rows=9456652 loops=1)
                           Merge Cond: (iquiza.quiz = qgo3.quiz)
                           Join Filter: (qgo3.groupid = gm.groupid)
                           ->  Merge Left Join  (cost=505.49..674178.59 rows=9483169 width=72) (actual time=0.716..11121.582 rows=9456652 loops=1)
                                 Merge Cond: (iquiza.quiz = qgo4.quiz)
                                 Join Filter: (qgo4.groupid = gm.groupid)
                                 ->  Nested Loop Left Join  (cost=491.10..641786.99 rows=9483169 width=64) (actual time=0.634..9216.211 rows=9456652 loops=1)
                                       ->  Merge Left Join  (cost=491.10..92943.52 rows=854943 width=64) (actual time=0.623..1033.513 rows=836894 loops=1)
                                             Merge Cond: (iquiza.quiz = quo.quiz)
                                             Join Filter: (quo.userid = iquiza.userid)
                                             ->  Merge Join  (cost=455.07..85106.29 rows=854943 width=48) (actual time=0.303..770.395 rows=836894 loops=1)
                                                   Merge Cond: (iquiz.id = iquiza.quiz)
                                                   ->  Index Scan using mdl_quiz_id_pk on mdl_quiz iquiz  (cost=0.00..3980.35 rows=14386 width=24) (actual time=0.068..15.953 rows=14298 loops=1)
                                                   ->  Index Scan using mdl_quizatte_qui_ix on mdl_quiz_attempts iquiza  (cost=0.00..70403.75 rows=854943 width=24) (actual time=0.011..515.468 rows=836894 loops=1)
                                             ->  Sort  (cost=36.04..37.43 rows=558 width=32) (actual time=0.319..20.696 rows=337767 loops=1)
                                                   Sort Key: quo.quiz
                                                   Sort Method:  quicksort  Memory: 64kB
                                                   ->  Seq Scan on mdl_quiz_overrides quo  (cost=0.00..10.58 rows=558 width=32) (actual time=0.009..0.098 rows=558 loops=1)
                                       ->  Index Scan using mdl_groumemb_use_ix on mdl_groups_members gm  (cost=0.00..0.50 rows=11 width=16) (actual time=0.003..0.008 rows=11 loops=836894)
                                             Index Cond: (gm.userid = iquiza.userid)
                                 ->  Sort  (cost=14.39..14.58 rows=77 width=24) (actual time=0.082..25.467 rows=404709 loops=1)
                                       Sort Key: qgo4.quiz
                                       Sort Method:  quicksort  Memory: 28kB
                                       ->  Seq Scan on mdl_quiz_overrides qgo4  (cost=0.00..11.98 rows=77 width=24) (actual time=0.004..0.052 rows=76 loops=1)
                                             Filter: (timelimit > 0)
                           ->  Sort  (cost=11.99..11.99 rows=2 width=24) (actual time=0.047..0.279 rows=2973 loops=1)
                                 Sort Key: qgo3.quiz
                                 Sort Method:  quicksort  Memory: 25kB
                                 ->  Seq Scan on mdl_quiz_overrides qgo3  (cost=0.00..11.98 rows=2 width=24) (actual time=0.022..0.042 rows=3 loops=1)
                                       Filter: (timelimit = 0)
                     ->  Sort  (cost=28.76..29.73 rows=390 width=24) (actual time=0.271..129.958 rows=2251399 loops=1)
                           Sort Key: qgo2.quiz
                           Sort Method:  quicksort  Memory: 45kB
                           ->  Seq Scan on mdl_quiz_overrides qgo2  (cost=0.00..11.98 rows=390 width=24) (actual time=0.004..0.121 rows=390 loops=1)
                                 Filter: (timeclose > 0)
               ->  Sort  (cost=12.10..12.12 rows=8 width=24) (actual time=0.068..0.277 rows=3118 loops=1)
        Sort Key: qgo1.quiz
                     Sort Method:  quicksort  Memory: 25kB
                     ->  Seq Scan on mdl_quiz_overrides qgo1  (cost=0.00..11.98 rows=8 width=24) (actual time=0.003..0.057 rows=8 loops=1)
                           Filter: (timeclose = 0)
 Total runtime: 42433.422 ms
(51 rows)