For MyISAM tables, Search operations
in nonspatial databases can be optimized using
SPATIAL indexes. This is true for spatial
databases as well. With the help of a great variety of
multi-dimensional indexing methods that have previously been
designed, it is possible to optimize spatial searches. The most
typical of these are:
Point queries that search for all objects that contain a given point
Region queries that search for all objects that overlap a given region
MySQL uses R-Trees with quadratic
splitting for SPATIAL indexes on
spatial columns. A SPATIAL index is built using
the MBR of a geometry. For most geometries, the MBR is a minimum
rectangle that surrounds the geometries. For a horizontal or a
vertical linestring, the MBR is a rectangle degenerated into the
linestring. For a point, the MBR is a rectangle degenerated into
the point.
It is also possible to create normal indexes on spatial columns.
In a non-SPATIAL index, you must declare a
prefix for any spatial column except for POINT
columns.
MyISAM supports both SPATIAL
and non-SPATIAL indexes. Other storage engines
support non-SPATIAL indexes, as described in
Section 12.1.11, “CREATE INDEX Syntax”.