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searching closest postcode using latitude longitude with mysql spatial type

Posted on 2012-03-27
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Last Modified: 2012-06-21
Using mysql db. I have a column "latlong" which is a point type with a spatial index. I would like to get the closest locations 4 miles closest to the latitude and longitude.

So far I have this...

SELECT `postcode`,county, ( 3959 * acos( cos( radians(51.585738) ) * cos( radians( x(GeomFromText(astext(latlong))) ) ) * cos( radians( y(GeomFromText(astext(latlong))) ) - radians(-0.260878) ) + sin( radians(51.585738) ) * sin( radians( x(GeomFromText(astext(latlong))) ) ) ) ) AS distance  
FROM uk_p HAVING distance < 4 ORDER BY distance LIMIT 0 , 20

 I only have 2900 records, and it takes approximately 0.0277 secs. Is there anyway of optimising this query, as I am worried that as the database grows, the slower this query will be...

Or does anyone know of any other approach that will be alot quicker?
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Question by:Rakz0r
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5 Comments
 
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Assisted Solution

by:HainKurt
HainKurt earned 250 total points
ID: 37773214
yes you can do this...
add a where condition and add

where
X(Geomfromtext(Astext(latlong))) between 51.585738 and 51.585738+4
and
Y(Geomfromtext(Astext(latlong))) between -0.260878 and -0.260878+4

what I think is, filter the data first before calculating the distance for all points...
hope it may improve it :)
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Author Comment

by:Rakz0r
ID: 37773284
I added the filter (below), and it does not bring up all the results that I expected. Anything wrong with this? Was expecting 14 records, but instead got 5 after adding this.

SELECT `postcode`,county, ( 3959 * acos( cos( radians(51.585738) ) * cos( radians( x(GeomFromText(astext(latlong))) ) ) * cos( radians( y(GeomFromText(astext(latlong))) ) - radians(-0.260878) ) + sin( radians(51.585738) ) * sin( radians( x(GeomFromText(astext(latlong))) ) ) ) ) AS distance  
FROM uk_p where X(Geomfromtext(Astext(latlong))) between 51.585738 and 51.585738+4 and Y(Geomfromtext(Astext(latlong))) between -0.260878 and -0.260878+4
 HAVING distance < 4 ORDER BY distance LIMIT 0 , 20
0
 

Author Comment

by:Rakz0r
ID: 37773319
I changed it slightly, but this only shedded off 0.0028 secs off the result. Any other ways to optimise this? Am i getting the latitude and longitude value correctly from the latlong column using x( GeomFromText( astext( latlong ))) ???

SELECT`postcode` , county, ( 3959 * acos( cos( radians( 51.585738))* cos( radians( x( GeomFromText( astext( latlong )))))* cos( radians( y( GeomFromText( astext( latlong ))))- radians(- 0.260878))+ sin( radians( 51.585738))* sin( radians( x( GeomFromText( astext( latlong )))))))AS distance
FROM uk_p
WHERE ( 3959 * acos( cos( radians( 51.585738))* cos( radians( x( GeomFromText( astext( latlong )))))* cos( radians( y( GeomFromText( astext( latlong ))))- radians(- 0.260878))+ sin( radians( 51.585738))* sin( radians( x( GeomFromText( astext( latlong )))))))<4
ORDER BY distance
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Accepted Solution

by:
Rakz0r earned 0 total points
ID: 37783484
ok I have managed to optimise it further.

instead of X(Geomfromtext(Astext(latlong))) to get the lat value from the point, simply use
x(latlong).

Original query was taking 0.0251 sec but now it takes 0.0035 sec with the query below.

So now I have...

SELECT`postcode` , county, ( 3959 * acos( cos( radians( 51.585738))* cos( radians( x( latlong )))* cos( radians( y( latlong ))- radians(- 0.260878))+ sin( radians( 51.585738))* sin( radians( x( latlong )))))AS distance
FROM uk_p
WHERE ( 3959 * acos( cos( radians( 51.585738))* cos( radians( x( latlong )))* cos( radians( y( latlong ))- radians(- 0.260878))+ sin( radians( 51.585738))* sin( radians( x( latlong )))))<4
ORDER BY distance
0
 

Author Closing Comment

by:Rakz0r
ID: 37800035
my answer gave the best optimisation
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