1.sql

"Limit  (cost=7462.23..7462.26 rows=10 width=404) (actual time=174.219..174.221 rows=10 loops=1)"
"  ->  Sort  (cost=7462.23..7588.10 rows=50345 width=404) (actual time=174.218..174.219 rows=10 loops=1)"
"        Sort Key: (count(loans.*))"
"        Sort Method: top-N heapsort  Memory: 27kB"
"        ->  GroupAggregate  (cost=0.00..6374.30 rows=50345 width=404) (actual time=0.036..153.099 rows=50285 loops=1)"
"              ->  Merge Left Join  (cost=0.00..5610.68 rows=52033 width=404) (actual time=0.019..106.530 rows=52034 loops=1)"
"                    Merge Cond: (users.id = loans.user_id)"
"                    ->  Index Scan using users_pkey on users  (cost=0.00..2486.07 rows=50345 width=97) (actual time=0.008..26.936 rows=50285 loops=1)"
"                    ->  Index Scan using index_loans_on_user_id on loans  (cost=0.00..2348.34 rows=52033 width=311) (actual time=0.007..30.102 rows=52034 loops=1)"
"Total runtime: 174.269 ms"

2.sql

"Nested Loop  (cost=4164.77..4247.75 rows=10 width=109) (actual time=35.290..35.316 rows=10 loops=1)"
"  ->  Limit  (cost=4164.77..4164.80 rows=10 width=4) (actual time=35.281..35.283 rows=10 loops=1)"
"        ->  Sort  (cost=4164.77..4287.86 rows=49234 width=4) (actual time=35.279..35.280 rows=10 loops=1)"
"              Sort Key: (count(*))"
"              Sort Method: top-N heapsort  Memory: 25kB"
"              ->  GroupAggregate  (cost=0.00..3100.84 rows=49234 width=4) (actual time=0.022..30.013 rows=50285 loops=1)"
"                    ->  Index Only Scan using index_loans_on_user_id on loans  (cost=0.00..2348.34 rows=52033 width=4) (actual time=0.017..16.110 rows=52034 loops=1)"
"                          Heap Fetches: 52034"
"  ->  Index Scan using users_pkey on users  (cost=0.00..8.28 rows=1 width=97) (actual time=0.002..0.002 rows=1 loops=10)"
"        Index Cond: (id = loans.user_id)"
"Total runtime: 35.358 ms"