Using Optimizer Hints in Rails

An execution plan describes a recommended method of execution for a SQL statement. The query optimizer attempts to generate the most optimal execution plan for a SQL statement.The optimizer chooses the plan with the lowest cost in terms of I/O, CPU, and communication. The database gathers these statistics about our objects like the number of rows, distinct values, and data distribution. The optimizer has such internal statistics and tools at its disposal which are used to calculate the said cost and pick an execution plan.