Spatial indexes

One of the defining characteristics of a spatial database is the ability to create special spatial indexes to speed up geometry-based searches. These indexes are used to perform spatial operations such as identifying all the features that lie within a given bounding box, identifying all the features within a certain distance of a given point, or identifying all the features that intersect with a given polygon.

A spatial index is defined in the same way as you define an ordinary database index, except that you add the SPATIAL keyword to identify the index as a spatial index. For example:

CREATE TABLE cities (
    id   INTEGER AUTO_INCREMENT PRIMARY KEY,
    name CHAR(255),
    geom POLYGON NOT NULL,

    INDEX (name),
    SPATIAL INDEX (geom))

All three open source spatial databases we will examine in this chapter implement spatial indexes using R-Tree data structures.

Note

PostGIS implements R-Trees using PostgreSQL's Generalized Search Tree (GiST) index type. Even though you...