この手順を最適化するには、助けが必要です。
DELIMITER $$
CREATE DEFINER=`ryan`@`%` PROCEDURE `GetCitiesInRadius`(
cityID numeric (15),
`range` numeric (15)
)
BEGIN
DECLARE lat1 decimal (5,2);
DECLARE long1 decimal (5,2);
DECLARE rangeFactor decimal (7,6);
SET rangeFactor = 0.014457;
SELECT `latitude`,`longitude` into lat1,long1
FROM world_cities as wc WHERE city_id = cityID;
SELECT
wc.city_id,
wc.accent_city as city,
s.state_name as state,
c.short_name as country,
GetDistance(lat1, long1, wc.`latitude`, wc.`longitude`) as dist
FROM world_cities as wc
left join states s on wc.state_id = s.state_id
left join countries c on wc.country_id = c.country_id
WHERE
wc.`latitude` BETWEEN lat1 -(`range` * rangeFactor) AND lat1 + (`range` * rangeFactor)
AND wc.`longitude` BETWEEN long1 - (`range` * rangeFactor) AND long1 + (`range` * rangeFactor)
AND GetDistance(lat1, long1, wc.`latitude`, wc.`longitude`) <= `range`
ORDER BY dist limit 6;
END
クエリの主要部分についての説明は次のとおりです。
+----+-------------+-------+--------+---------------+--------------+---------+--------------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+---------------+--------------+---------+--------------------------+------+----------------------------------------------+
| 1 | SIMPLE | B | range | idx_lat_long | idx_lat_long | 12 | NULL | 7619 | Using where; Using temporary; Using filesort |
| 1 | SIMPLE | s | eq_ref | PRIMARY | PRIMARY | 4 | civilipedia.B.state_id | 1 | |
| 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 1 | civilipedia.B.country_id | 1 | Using where |
+----+-------------+-------+--------+---------------+--------------+---------+--------------------------+------+----------------------------------------------+
3 rows in set (0.00 sec)
インデックスは次のとおりです。
mysql> show indexes from world_cities;
+--------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+--------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| world_cities | 0 | PRIMARY | 1 | city_id | A | 3173958 | NULL | NULL | | BTREE | |
| world_cities | 1 | country_id | 1 | country_id | A | 23510 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | city | 1 | city | A | 3173958 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | accent_city | 1 | accent_city | A | 3173958 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | idx_pop | 1 | population | A | 28854 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | idx_lat_long | 1 | latitude | A | 1057986 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | idx_lat_long | 2 | longitude | A | 3173958 | NULL | NULL | YES | BTREE | |
| world_cities | 1 | accent_city_2 | 1 | accent_city | NULL | 1586979 | NULL | NULL | YES | FULLTEXT | |
+--------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
8 rows in set (0.01 sec)
クエリに表示される関数は、速度低下の原因になるとは思いませんが、関数は次のとおりです。
CREATE DEFINER=`ryan`@`%` FUNCTION `GetDistance`(lat1 numeric (9,6),
lon1 numeric (9,6),
lat2 numeric (9,6),
lon2 numeric (9,6) ) RETURNS decimal(10,5)
BEGIN
DECLARE x decimal (20,10);
DECLARE pi decimal (21,20);
SET pi = 3.14159265358979323846;
SET x = sin( lat1 * pi/180 ) * sin( lat2 * pi/180 ) + cos(
lat1 *pi/180 ) * cos( lat2 * pi/180 ) * cos( (lon2 * pi/180) -
(lon1 *pi/180)
);
SET x = atan( ( sqrt( 1- power( x, 2 ) ) ) / x );
RETURN ( 1.852 * 60.0 * ((x/pi)*180) ) / 1.609344;
END