http://openlife.cc/blogs/2012/august/comparing-open-source-gis-implementations
https://segmentfault.com/q/1010000000345194/a-1020000000345429
http://www.infoq.com/cn/articles/depth-study-of-Symfony2
简单列举一下已经了解到的方案：
1.sphinx geo索引
2.mongodb geo索引
3.mysql sql查询
4.mysql+geohash
5.redis+geohash
6.postGIS+Elasticsearch
