Preferred query plans for user-response-time optimization

When the optimizer chooses query plans to optimize user-response time, it computes the cost for retrieving the first row in the query for each plan and chooses the plan with the lowest cost. In some cases, the query plan with the lowest cost for retrieving the first row might not be the optimal path to retrieve all rows in the query.

The following sections explain some of the possible differences in query plans.


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