我有两张表:一张包含点,另一张包含多边形。
CREATE TABLE `points` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`point` point NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM;
CREATE TABLE `ranges` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`poly` polygon NOT NULL,
PRIMARY KEY (`id`),
SPATIAL KEY `poly` (`poly`)
) ENGINE=MyISAM;
我想将范围连接到多边形内部的点上。查询看起来很简单:
SELECT *
FROM points
LEFT JOIN ranges
ON MBRCONTAINS(poly, point)
WHERE points.id = 2;
这个查询非常快且使用索引,部分的执行计划如下:
table | type | possible_keys | key | key_len ranges | range | poly | poly | 34
但是,当我尝试与表格points
中的多行进行连接时:
SELECT *
FROM points
LEFT JOIN ranges
ON MBRCONTAINS(poly, point)
WHERE points.id IN (1,2,3);
一切都崩溃了:
+----+-------------+------------+-------+---------------+---------+---------+------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+-------+---------------+---------+---------+------+--------+-------------+ | 1 | SIMPLE | points | range | PRIMARY | PRIMARY | 4 | NULL | 3 | Using where | | 1 | SIMPLE | ranges | ALL | poly | NULL | NULL | NULL | 155183 | | +----+-------------+------------+-------+---------------+---------+---------+------+--------+-------------+
添加 FORCE INDEX (poly)
没有起到帮助作用。
用于测试查询的样本数据(抱歉,只提供php版本,我不熟悉SQL程序):
//points
for($i=0;$i<=500;$i++) {
$point = mt_rand();
mysql_query('INSERT INTO points (point) VALUES (POINTFROMWKB(POINT('.$point.', 0)))');
}
$qty = 20000;
$max = mt_getrandmax();
$add = $max / $qty
$end = 0;
//polys
while($end < $max) {
$start = $end;
$end = mt_rand($start, $start + $add);
mysql_query('INSERT INTO ranges (poly) VALUES (
GEOMFROMWKB(POLYGON(LINESTRING(
POINT('.$start.', -1),
POINT('.$end.', -1),
POINT('.$end.', 1),
POINT('.$start.', 1),
POINT('.$start.', -1)
)))
)');
}