Oracle Database - The Query Plan Estimator


The estimator is involved in the query optimizer process. Its main task is to measure the plans that give the plan generator.

It generates three different types of measures :

These measures are related to each other, and one is derived from another.

The end goal of the estimator is to estimate the overall cost of a given plan. If statistics are available, then the estimator uses them to compute the measures. The statistics improve the degree of accuracy of the measures.

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