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- <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 70. How the Planner Uses Statistics</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="bki-example.html" title="69.6. BKI Example" /><link rel="next" href="row-estimation-examples.html" title="70.1. Row Estimation Examples" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 70. How the Planner Uses Statistics</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="bki-example.html" title="69.6. BKI Example">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="internals.html" title="Part VII. Internals">Up</a></td><th width="60%" align="center">Part VII. Internals</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="row-estimation-examples.html" title="70.1. Row Estimation Examples">Next</a></td></tr></table><hr></hr></div><div class="chapter" id="PLANNER-STATS-DETAILS"><div class="titlepage"><div><div><h2 class="title">Chapter 70. How the Planner Uses Statistics</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="row-estimation-examples.html">70.1. Row Estimation Examples</a></span></dt><dt><span class="sect1"><a href="multivariate-statistics-examples.html">70.2. Multivariate Statistics Examples</a></span></dt><dd><dl><dt><span class="sect2"><a href="multivariate-statistics-examples.html#FUNCTIONAL-DEPENDENCIES">70.2.1. Functional Dependencies</a></span></dt><dt><span class="sect2"><a href="multivariate-statistics-examples.html#MULTIVARIATE-NDISTINCT-COUNTS">70.2.2. Multivariate N-Distinct Counts</a></span></dt><dt><span class="sect2"><a href="multivariate-statistics-examples.html#MCV-LISTS">70.2.3. MCV Lists</a></span></dt></dl></dd><dt><span class="sect1"><a href="planner-stats-security.html">70.3. Planner Statistics and Security</a></span></dt></dl></div><p>
- This chapter builds on the material covered in <a class="xref" href="using-explain.html" title="14.1. Using EXPLAIN">Section 14.1</a> and <a class="xref" href="planner-stats.html" title="14.2. Statistics Used by the Planner">Section 14.2</a> 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.
- </p><p>
- 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.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bki-example.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="internals.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="row-estimation-examples.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">69.6. BKI Example </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 70.1. Row Estimation Examples</td></tr></table></div></body></html>
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