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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>65.1. Introduction</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="spgist.html" title="Chapter 65. SP-GiST Indexes" /><link rel="next" href="spgist-builtin-opclasses.html" title="65.2. Built-in Operator Classes" /></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">65.1. Introduction</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="spgist.html" title="Chapter 65. SP-GiST Indexes">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="spgist.html" title="Chapter 65. SP-GiST Indexes">Up</a></td><th width="60%" align="center">Chapter 65. SP-GiST Indexes</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="spgist-builtin-opclasses.html" title="65.2. Built-in Operator Classes">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="SPGIST-INTRO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">65.1. Introduction</h2></div></div></div><p>
- <acronym class="acronym">SP-GiST</acronym> is an abbreviation for space-partitioned
- <acronym class="acronym">GiST</acronym>. <acronym class="acronym">SP-GiST</acronym> supports partitioned
- search trees, which facilitate development of a wide range of different
- non-balanced data structures, such as quad-trees, k-d trees, and radix
- trees (tries). The common feature of these structures is that they
- repeatedly divide the search space into partitions that need not be
- of equal size. Searches that are well matched to the partitioning rule
- can be very fast.
- </p><p>
- These popular data structures were originally developed for in-memory
- usage. In main memory, they are usually designed as a set of dynamically
- allocated nodes linked by pointers. This is not suitable for direct
- storing on disk, since these chains of pointers can be rather long which
- would require too many disk accesses. In contrast, disk-based data
- structures should have a high fanout to minimize I/O. The challenge
- addressed by <acronym class="acronym">SP-GiST</acronym> is to map search tree nodes to
- disk pages in such a way that a search need access only a few disk pages,
- even if it traverses many nodes.
- </p><p>
- Like <acronym class="acronym">GiST</acronym>, <acronym class="acronym">SP-GiST</acronym> is meant to allow
- the development of custom data types with the appropriate access methods,
- by an expert in the domain of the data type, rather than a database expert.
- </p><p>
- Some of the information here is derived from Purdue University's
- SP-GiST Indexing Project
- <a class="ulink" href="https://www.cs.purdue.edu/spgist/" target="_top">web site</a>.
- The <acronym class="acronym">SP-GiST</acronym> implementation in
- <span class="productname">PostgreSQL</span> is primarily maintained by Teodor
- Sigaev and Oleg Bartunov, and there is more information on their
-
- <a class="ulink" href="http://www.sai.msu.su/~megera/wiki/spgist_dev" target="_top">web site</a>.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="spgist.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spgist.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="spgist-builtin-opclasses.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 65. SP-GiST Indexes </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 65.2. Built-in Operator Classes</td></tr></table></div></body></html>
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