Metric Name	Value	Desc
estimated-cost	20902.40
estimated-rows-read	24,007	16005 rows from the table "rental". A table scan ( "access_type": "ALL" ). The optimizer thinks 50% of the rows ("filtered": "50.00") are relevant for the WHERE clause, which means 8002 rows ( "rows_produced_per_join": 8002). Then it uses "access_type": "eq_ref" to get the relevant rows, 8002 times (using the index of the Primary Key, called "PRIMARY"). The Optimizer has wrong expectations as 15,682 rows match the condition (90% more)
estimated-rows-returned	8002	16005 rows from the table "rental". A table scan ( "access_type": "ALL" ). The optimizer thinks 50% of the rows ("filtered": "50.00") are relevant for the WHERE clause, which means 8002 rows ( "rows_produced_per_join": 8002). Then it uses "access_type": "eq_ref" to get the relevant rows, 8002 times (using the index of the Primary Key, called "PRIMARY").
total-sort-operation-costs	8002.0	"cost_info": { "sort_cost": "8002.00"},
total-num-of-rows-sorted	8002	Use the estimated rows returned. Same number was sorted.