Oracle Database - The Query Plan Estimator

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Table of Contents

1 - About

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.