# See the 10 SELECT queries which touch the most number of rows.
# These queries may benefit from adding indexes to reduce the number
# of rows retrieved/affected.
SELECT
  rows, # rows is the number of rows retrieved/affected by the query
  query
FROM pg_stat_statements
WHERE query iLIKE '%SELECT%'
ORDER BY rows DESC
LIMIT 10;

#  query   |  rows 
#  --------+--------
#  SELECT  |  701724
#  SELECT  |  284772
#  SELECT  |  233914
#  SELECT  |  196424
#  SELECT  |  164421
#  SELECT  |  164419
#  SELECT  |  164419
#  SELECT  |  164419
#  SELECT  |  138395
#  SELECT  |  117636
#  (10 rows)