Select * from City where Population between 731200 The CPU cost is based on evaluating query conditions, comparing keys/records and sorting keys. IO is estimated in pages read from table and pages read from index.The IO cost is estimates from storage engine based on number of pages to read.The cost unit is calculated form executing query read a random data pages. The cost for executing a query below this method used. It represents the cost of reading an index or data block from an memory database buffer. The default value is (1.0),it’s similar to io_block_read_cost.The default value of io_block_read_cost is (1.0).It will reading an index or data block from disk.It’s intended for specifying storage devices like hard drives (vs) solid state drives.If the value is default it applies all storage engines. The name of the storage engine this cost estimate applied.It estimates the operations specific for particular storage engines.It’s a descriptive comment associated with cost model.It show’s time of the last row updated.Otherwise it use’s default estimate value. If the value is not null the server use’s the cost.The name of a cost estimate used in cost-model,it’s not case sensitive. The server_cost estimates general server operations.The server_cost contain these columns.The MySQL system database contain cost estimate information tables inside MySQL schema. These cost estimates are stored in server_cost & engine_cost tables in MySQL schema.In MySQL 5.7, the optimizer has addition a database of cost estimates to use during the execution plan.
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