How did you populate the point column? Should be something like:
UPDATE places SET point= =GeomFromText(CONCAT("Point(",longitude,"
",latitude,")"));
You also should have a spatial index:
ALTER TABLE places MODIFY coordinates point NOT NULL, add spatial index
(coordinates);
You can check the data with the ASTEXT() function:
SELECT longitude, latitude, ASTEXT(coordinates) FROM places;
Hope this helps
-Gavin Towey
From: René Fournier [mailto:m...@renefournier.com]
Sent: Saturday, December 19, 2009 12:42 AM
To: Gavin Towey
Cc: mysql
Subject: Re: Spatial extensions
Thanks Gavin.
I've got part your query working... sort of. Something I can't figure out is
how to use MBRContains on a table with a POINT column. For example, this works:
mysql> select id, astext(coordinates) FROM places where
MBRContains(GeomFromText('POLYGON((48.6 -116.4,53.4 -116.4,53.4 -111.6,48.6
-111.6,48.6 -116.4))'), GeomFromText('Point(49 -114)')) limit 10;
+----+----------------------------------+
| id | astext(coordinates) |
+----+----------------------------------+
| 1 | POINT(49.00701238 -110.00507933) |
| 2 | POINT(49.01415809 -110.01615511) |
| 3 | POINT(49.01424023 -110.00508075) |
| 4 | POINT(48.99978158 -110.01617366) |
| 5 | POINT(48.99978996 -110.00507794) |
| 6 | POINT(49.00683419 -110.02751996) |
| 7 | POINT(49.01402057 -110.03861578) |
| 8 | POINT(49.01407281 -110.02750442) |
| 9 | POINT(48.99974667 -110.0386263) |
| 10 | POINT(48.9997718 -110.0275421) |
+----+----------------------------------+
10 rows in set (0.00 sec)
But when I try to use the table's POINT column, nothing is returned:
mysql> select id, astext(coordinates) FROM places where
MBRContains(GeomFromText('POLYGON((48.6 -116.4,53.4 -116.4,53.4 -111.6,48.6
-111.6,48.6 -116.4))'), (coordinates)) limit 10;
Empty set (0.00 sec)
What am I missing? For clarity, here's the table schema:
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;
On 2009-12-18, at 2:21 AM, Gavin Towey wrote:
Not only is it 5.1, but there's a special branch that has improved GIS
functions not found in the regular MySQL. I'm not sure if/when they're
planning on rolling them back into mysql:
http://downloads.mysql.com/forge/mysql-5.1.35-gis/
If it's not possible to use that version, then you can still implement a
Distance function yourself as a stored procedure or UDF. Just google for
mysql+haversine or something similar.
The important part though is the MBRContains, which does an efficient box cull
and uses the spatial index. Oops, I forgot to change a couple occurances of
"line_segment" to "coordinates" line_segment was just the column name I was
using in my original query.
Regards,
Gavin Towey
-----Original Message-----
From: René Fournier [mailto:m...@renefournier.com]
Sent: Thursday, December 17, 2009 8:54 AM
To: Gavin Towey
Cc: mysql
Subject: Re: Spatial extensions
Awesome, this is what I was trying to find, as you succinctly wrote it. I
*really* appreciate getting pointed in the right direction, since I haven't
found a lot of MySQL's GIS tutorials directed at what I'm trying to do.
Still, a couple questions, the Distance() function you included, that must
require 5.1 or higher right? 5.0.88 on my box throws an error:
"Function places.Distance does not exist"
Also, where does line_segment come from in the below query?
Thanks.
...Rene
On 2009-12-17, at 8:45 AM, Gavin Towey wrote:
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:m...@renefournier.com]
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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