From Ingres Community Wiki

Optimizer Facility Overview

Introduction

The Optimizer Facility (OPF) is one of the major components of the Ingres database server. It is responsible for transforming a parsed query into an executable query plan. This transformation includes the phases one would expect from a state of the art commercial query optimizer including query rewrite and cost based plan generation. This document discusses the architecture of OPF in detail sufficient to enable a dbms practitioner to understand its major control structures and flow of control.

More Detailed Information

Note that this document is a work-in-progress. Numerous sections have been laid out but not yet filled in. More will be added to this document over time.