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使用 Rails 3.2、Ruby 1.9、geocoder gem。我的控制器中有以下查询：

# 1500+ms to load
nearby_shops = (current_shop.nearbys(10, :order => 'overall_rating DESC')
.where(:shop_type => shop_type).includes(:photos, :active_property_list => 
:hotel_image_lists).limit(5))

# SQL
Shop Load (4045.6ms)  SELECT shops.*, 3958.755864232 * 2 * ASIN(SQRT(POWER(
SIN((36.111927 - shops.lat) * PI() / 180 / 2), 2) + COS(36.111927 * PI()
 / 180) * COS(shops.lat * PI() / 180) * POWER(SIN((-115.171229 - shops.lng)
 * PI() / 180 / 2), 2))) AS distance, CAST(DEGREES(ATAN2( RADIANS(shops.lng
 - -115.171229), RADIANS(shops.lat - 36.111927))) + 360 AS decimal) % 360 AS
 bearing FROM `shops` WHERE `shops`.`shop_type` = 'food' AND (shops.lat BETWEEN
 35.96719521688915 AND 36.25665878311085 AND shops.lng BETWEEN
 -115.3503819353204 AND -114.9920760646796 AND 3958.755864232 * 2 * 
ASIN(SQRT(POWER(SIN((36.111927 - shops.lat) * PI() / 180 / 2), 2) + 
COS(36.111927 * PI() / 180) * COS(shops.lat * PI() / 180) * POWER(SIN((
-115.171229 - shops.lng) * PI() / 180 / 2), 2))) <= 10 AND shops.id != 85155)
 ORDER BY overall_rating DESC LIMIT 5
 - shops.lat) * PI() / 180 / 2), 2) + COS(48.8582411618 * PI() / 180) * 
COS(shops.lat * PI() / 180) * POWER(SIN((2.2945044899 - shops.lng) * PI() / 
180 / 2), 2))) <= 100 AND shops.id != 517) ORDER BY distance ASC LIMIT 25
 OFFSET 0

问题在于对和nearbys进行计算。我已经为和列添加了索引，但它没有任何改进。longitudelatitudelongitudelatitude

我该如何改进呢？

P/S：我删除了不影响查询速度的无关条件。

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1 回答 1

0

这可能不是最精确或最优雅的解决方案，但为什么不稍微捏造一下数学。您可以编写一个执行如下操作的 select 子句：

 .select(["id, name, 69.0975851*sqrt(POWER(shops.lat-?,2) + COS(?*PI()/180)*POWER(shops.lon-?,2)) AS DISTANCE", loc.lat, loc.lat, loc.lon])

如果您只是处理小的（< 500 英里）距离，您实际上并不需要使用那个毛茸茸的大圆圈公式。您最终会以一小部分计算成本得到相同的〜几乎〜答案。

于 2013-10-02T19:47:04.510 回答