For InnoDB
and MyISAM
tables, MySQL can create spatial indexes using syntax similar to
that for creating regular indexes, but using the
SPATIAL
keyword. Columns in spatial indexes
must be declared NOT NULL
. The following
examples demonstrate how to create spatial indexes:
With
CREATE TABLE
:CREATE TABLE geom (g GEOMETRY NOT NULL SRID 4326, SPATIAL INDEX(g));
With
ALTER TABLE
:CREATE TABLE geom (g GEOMETRY NOT NULL SRID 4326); ALTER TABLE geom ADD SPATIAL INDEX(g);
With
CREATE INDEX
:CREATE TABLE geom (g GEOMETRY NOT NULL SRID 4326); CREATE SPATIAL INDEX g ON geom (g);
SPATIAL INDEX
creates an R-tree index. For
storage engines that support nonspatial indexing of spatial
columns, the engine creates a B-tree index. A B-tree index on
spatial values is useful for exact-value lookups, but not for
range scans.
The optimizer can use spatial indexes defined on columns that are SRID-restricted. For more information, see Section 13.4.1, “Spatial Data Types”, and Section 10.3.3, “SPATIAL Index Optimization”.
For more information on indexing spatial columns, see Section 15.1.15, “CREATE INDEX Statement”.
To drop spatial indexes, use ALTER
TABLE
or DROP INDEX
:
With
ALTER TABLE
:ALTER TABLE geom DROP INDEX g;
With
DROP INDEX
:DROP INDEX g ON geom;
Example: Suppose that a table geom
contains
more than 32,000 geometries, which are stored in the column
g
of type GEOMETRY
. The
table also has an AUTO_INCREMENT
column
fid
for storing object ID values.
mysql> DESCRIBE geom;
+-------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+----------------+
| fid | int(11) | | PRI | NULL | auto_increment |
| g | geometry | | | | |
+-------+----------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
mysql> SELECT COUNT(*) FROM geom;
+----------+
| count(*) |
+----------+
| 32376 |
+----------+
1 row in set (0.00 sec)
To add a spatial index on the column g
, use
this statement:
mysql> ALTER TABLE geom ADD SPATIAL INDEX(g);
Query OK, 32376 rows affected (4.05 sec)
Records: 32376 Duplicates: 0 Warnings: 0