Book Image

PostGIS Cookbook - Second Edition

By : Pedro Wightman, Bborie Park, Stephen Vincent Mather, Thomas Kraft, Mayra Zurbarán
Book Image

PostGIS Cookbook - Second Edition

By: Pedro Wightman, Bborie Park, Stephen Vincent Mather, Thomas Kraft, Mayra Zurbarán

Overview of this book

PostGIS is a spatial database that integrates the advanced storage and analysis of vector and raster data, and is remarkably flexible and powerful. PostGIS provides support for geographic objects to the PostgreSQL object-relational database and is currently the most popular open source spatial databases. If you want to explore the complete range of PostGIS techniques and expose related extensions, then this book is for you. This book is a comprehensive guide to PostGIS tools and concepts which are required to manage, manipulate, and analyze spatial data in PostGIS. It covers key spatial data manipulation tasks, explaining not only how each task is performed, but also why. It provides practical guidance allowing you to safely take advantage of the advanced technology in PostGIS in order to simplify your spatial database administration tasks. Furthermore, you will learn to take advantage of basic and advanced vector, raster, and routing approaches along with the concepts of data maintenance, optimization, and performance, and will help you to integrate these into a large ecosystem of desktop and web tools. By the end, you will be armed with all the tools and instructions you need to both manage the spatial database system and make better decisions as your project's requirements evolve.
Table of Contents (18 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Using indexes


A database index is very much like the index of a book (such as this one). While a book's index indicates the pages on which a word is present, a database column index indicates the rows in a table that contain a searched-for value. Just as a book's index does not indicate exactly where on the page a word is located, the database index may not be able to denote the exact location of the searched-for value in a row's column.

PostgreSQL has several types of index, such as B-Tree, Hash, GIST, SP-GIST, and GIN. All of these index types are designed to help queries find matching rows faster. What makes the indices different are the underlying algorithms. Generally, to keep things simple, almost all PostgreSQL indexes are of the B-Tree type. PostGIS (spatial) indices are of the GIST type.

Geometries, geographies, and rasters are all large, complex objects, and relating to or among these objects takes time. Spatial indices are added to the PostGIS data types to improve search performance...