问题
Recently I'm using GeoHash to hash the paired geo-coordinates into a hash value and store it in MySQL. Now I want to find the nearest hash given the other hash. I noticed that MYSQL provide BTree structure to find a range of nearest hashes by using the command "like" in SQL query.
The problem is, how could I find the nearest one instead of giving a range since sometimes I don't know the range.
Could someone give me a hint?
Really appreciate it.
回答1:
QuadTile (or GeoHash?) reversibly turns latitude + longitude into a single number. But to use it to "find nearest" gets complex and messy. Read about Z-ordering. As I understand it, you would need to run 4 queries with ORDER BY and LIMIT; UNION the results together; then check to see which are best.
But it gets tricky to know what to do if the attempt did not find enough items.
SPATIAL indexes provide a more straightforward way.
Here is a technique for efficiently "finding nearest" for large datasets.
来源：https://stackoverflow.com/questions/52229304/how-to-find-the-nearest-geohash-in-mysql