Chapter 69. How the Planner Uses Statistics

   Table of Contents

   69.1. Row Estimation Examples
   69.2. Multivariate Statistics Examples

        69.2.1. Functional Dependencies
        69.2.2. Multivariate N-Distinct Counts
        69.2.3. MCV Lists

   69.3. Planner Statistics and Security

   This chapter builds on the material covered in Section 14.1 and
   Section 14.2 to show some additional details about how the planner uses
   the system statistics to estimate the number of rows each part of a
   query might return. This is a significant part of the planning process,
   providing much of the raw material for cost calculation.

   The intent of this chapter is not to document the code in detail, but
   to present an overview of how it works. This will perhaps ease the
   learning curve for someone who subsequently wishes to read the code.