Hi Gavin,
OK, I finally tracked down the source of the trouble... My CREATE TABLE query
included a regular KEY index instead of SPATIAL KEY -- that's why the
MBRCONTAINS wasn't working... Works now!!
Thanks for your help.
On 2009-12-22, at 2:42 AM, Gavin Towey wrote:
> 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:[email protected]]
> 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:[email protected]]
> 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:[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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