Yes, spatial indexes are very fast:
Query would be something like:
SET @center = GeomFromText('POINT(37.372241 -122.021671)');
SET @radius = 0.005;
SET @bbox = GeomFromText(CONCAT('POLYGON((',
X(@center) - @radius, ' ', Y(@center) - @radius, ',',
X(@center) + @radius, ' ', Y(@center) - @radius, ',',
X(@center) + @radius, ' ', Y(@center) + @radius, ',',
X(@center) - @radius, ' ', Y(@center) + @radius, ',',
X(@center) - @radius, ' ', Y(@center) - @radius, '))')
);
select id, astext(coordinates), Distance(@center,line_segment) as dist
FROM places where MBRContains(@bbox, line_segment) order by dist limit 10;
Regards,
Gavin Towey
-----Original Message-----
From: René Fournier [mailto:[email protected]]
Sent: Wednesday, December 16, 2009 4:32 PM
To: mysql
Subject: Spatial extensions
I have table with 2 million rows of geographic points (latitude, longitude).
Given a location -- say, 52º, -113.9º -- what's the fastest way to query the 10
closest points (records) from that table? Currently, I'm using a simple
two-column index to speed up queries:
CREATE TABLE `places` (
`id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
`latitude` decimal(10,8) NOT NULL,
`longitude` decimal(12,8) NOT NULL
PRIMARY KEY (`id`),
KEY `latlng` (`latitude`,`longitude`)
) ENGINE=MyISAM AUTO_INCREMENT=50 DEFAULT CHARSET=latin1
COLLATE=latin1_general_ci;
My current query is fairly quick:
SELECT SQL_NO_CACHE * FROM places WHERE latitude BETWEEN 51.98228037384 AND
52.033153677 AND longitude BETWEEN -113.94770681881 AND -113.86685484296;
But I wonder a couple things:
1. Would MySQL's [seemingly anemic] spatial extensions would speed things up if
I added a column of type POINT (and a corresponding spatial INDEX)?
CREATE TABLE `places` (
`id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
`latitude` decimal(10,8) NOT NULL,
`longitude` decimal(12,8) NOT NULL,
`coordinates` point NOT NULL,
PRIMARY KEY (`id`),
KEY `latlng` (`latitude`,`longitude`),
KEY `coord` (`coordinates`(25))
) ENGINE=MyISAM AUTO_INCREMENT=50 DEFAULT CHARSET=latin1
COLLATE=latin1_general_ci;
2. How would I write the query?
...Rene
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