Question

使用Rails 3.2，Ruby 1.9，geocoder gem。我在控制器中的以下查询：

# 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nearbys，它会对longitude和latitude进行计算。我已经为longitude和latitude列添加了索引，但它没有改进任何内容。

我该如何改善这个？

P / S：我删除了无关条件，这些条件对查询速度没有贡献。

Answer 1

这可能不是最精确或最优雅的解决方案，但为什么不只是略微捏造数学。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])

如果你只是处理小（<500英里）的距离，你真的不需要使用那个毛茸茸的大圆公式。你最终会得到相同的〜几乎〜答案的一小部分计算成本。

Ruby Geocoder附近很慢

1 个答案: