从mysql数据库中选择最近的地理位置的最快方法是什么? [英] What is the fastest way to select nearest geographical place from mysql database?
问题描述
我在mysql数据库中有一个表，其中包含地理坐标和其他有关地点的信息.表格中的每一行代表一个地理位置，并具有以下坐标:纬度= 45.05235和经度= 8.02354，这是欧洲的某个地方.
I have a table in a mysql database containing geo coordinates and other information about places. Each row in the table represents a geographical place and has coordinates such as: Latitude = 45.05235 and Longitude = 8.02354 which is a place somewhere in Europe.
考虑到某些输入的地理坐标(相同格式)，我需要从该表中选择最近的地方，或某个半径范围内的最近的地方.
Given on some input geographical coordinates (same format) I need to select from that table the nearest place, or the nearest places within some radius.
我已经在使用索引，但是由于这些函数已被多次使用，因此我想加快这一过程.
I'm already using indices, however I want to speed up the process since these functions are used many times.
如果我可以通过一个查询直接选择最近的地点或某个半径范围内的地点，这可能会有所帮助.当然，任何其他解决方案也都非常受欢迎.
It might help if I could select the nearest place or places within a certain radius directly with one query. Any other solutions are also very welcom of course.
我制作了一个可以获取最近位置的函数(该函数可以运行，但是速度很慢):
I made a function that gets the nearest place (which is working but slow):
<?php
//Function for getting nearest destinations:
function nearest_destination($lat1,$lon1,$radius,$type,$maxdistance){
//Determine geo bounds:
$lonlow = $lon1 - rad2deg($maxdistance/6371);
$lonhigh = $lon1 + rad2deg($maxdistance/6371);
$latlow = $lat1 - rad2deg($maxdistance/6371);
$lathigh = $lat1 + rad2deg($maxdistance/6371);
//Database details and connect to database
include(realpath($_SERVER["DOCUMENT_ROOT"]).'/connect_to_db.php');
//Set initial counters to zero
$ii=0;
$i=0;
while($row = mysql_fetch_array($result, MYSQL_ASSOC)){
$shortnamelist[$ii]=$row['shortname'];
$fullnamelist[$ii]=$row['fullname'];
$latitudelist[$ii]=$row['latitude'];
$longitudelist[$ii]=$row['longitude'];
$lon2=$row['longitude'];
$lat2=$row['latitude'];
//Calculate the distance:
$delta_lon = $lon2 - $lon1;
$earth_radius = "6371"; # in km
$distance = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($delta_lon)) ;
$distance = acos($distance);
$distance = $earth_radius*$distance;
$distance = round($distance, 4);
$distancelist[$ii] = $distance;
$ii=$ii+1;
}
//Select position of nearest, and select the destination
if(isset($distancelist)){
$minkey=array_keys($distancelist, min($distancelist));
$minkey=$minkey[0];
$fullname=$fullnamelist[$minkey];
$shortname=$shortnamelist[$minkey];
$latitude=$latitudelist[$minkey];
$longitude=$longitudelist[$minkey];
// remove the big arrays to conserve memory:
unset($fullnamelist);
unset($latitudelist);
unset($longitudelist);
unset($distancelist);
unset($shortnamelist);
}
if(isset($destinid)=='TRUE'){
$nearest_destination = array("shortname" => $shortname, "fullname" => $fullname, "latitude" => $latitude, "longitude" => $longitude, "distancelist" => $distancelisting);}
else $nearest_destination = 0;
mysql_close ();
return $nearest_destination;
}
?>
此功能可以选择某个半径范围内最近的位置(有效但较慢):
This is the function that selects the nearest places within a certain radius (working but slow):
<?php
//Function for getting nearest destinations:
function nearest_destination($lat1,$lon1,$radius,$type,$maxdistance){
//Determine geo bounds:
$lonlow = $lon1 - rad2deg($maxdistance/6371);
$lonhigh = $lon1 + rad2deg($maxdistance/6371);
$latlow = $lat1 - rad2deg($maxdistance/6371);
$lathigh = $lat1 + rad2deg($maxdistance/6371);
// Convert from string to number:
$lon1=floatval($lon1);
$lat1=floatval($lat1);
//Database details and connect to database
include(realpath($_SERVER["DOCUMENT_ROOT"]).'/connect_to_database.php'); //Get DB login details
//Select data from destinations table:
$sql="SELECT shortname, fullname, latitude, longitude FROM destinations WHERE type='$type' AND longitude > $lonlow AND longitude < $lonhigh AND latitude > $latlow AND latitude < $lathigh";
$result=mysql_query($sql);
//Set initial counter to zero
$i=0;
while($row = mysql_fetch_array($result, MYSQL_ASSOC)){
$lon2=$row['longitude'];
$lat2=$row['latitude'];
$lon2=floatval($lon2);
$lat2=floatval($lat2);
//Calculate the distance:
$delta_lon = $lon2 - $lon1;
$earth_radius = "6371"; # in km
$distance = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($delta_lon)) ;
$distance = acos($distance);
$distance = $earth_radius*$distance;
$distance = round($distance, 4);
//If distance is smaller than the radius the destination is saved in the array:
if($distance<$radius){
$fullname[$i]=$row['fullname'];
$shortname[$i]=$row['shortname'];
$latitude[$i]=$row['latitude'];
$longitude[$i]=$row['longitude'];
$distancelisting[$i] = $distance;
$i=$i+1;
}
}
if(isset($destinid)=='TRUE'){
$nearest_destination = array("shortname" => $shortname, "fullname" => $fullname, "latitude" => $latitude, "longitude" => $longitude, "distancelist" => $distancelisting);}
else $nearest_destination = 0;
mysql_close ();
return $nearest_destination;
}
?>
推荐答案
随时根据需要进行修改:
Feel free to modify as needed:
<?php
$center_lat = $_GET["lat"];
$center_lng = $_GET["lng"];
$radius = $_GET["radius"];
$unit = $_GET["unit"];
$unitConst = $unit == "mi" ? 3959 : 6371;
$sql = sprintf("SELECT Address, City, State, Country, PostalCode, PhoneNumber, Lat, Lng, ($unitConst * acos(cos(radians('%s')) * cos(radians(Lat)) * cos(radians(Lng) - radians('%s')) + sin(radians('%s')) * sin(radians(Lat)))) AS Distance FROM destinations WHERE (Lat != '0' AND Lng !=0) HAVING distance < '%s' ORDER BY distance", mysql_real_escape_string($center_lat), mysql_real_escape_string($center_lng), mysql_real_escape_string($center_lat), mysql_real_escape_string($radius));
?>
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