updated r-tree to support 20 dimensions

README.md

@@ -30,11 +30,11 @@ Features
 
 - In-memory database for [fast reads and writes](https://github.com/tidwall/raft-boltdb#benchmarks)
 - Embeddable with a [simple API](https://godoc.org/github.com/tidwall/buntdb)
-- [Spatial indexing](#spatial-indexes) for up to 4 dimensions; Useful for Geospatial data
+- [Spatial indexing](#spatial-indexes) for up to 20 dimensions; Useful for Geospatial data
 - Create [custom indexes](#custom-indexes) for any data type
 - [Built-in types](#built-in-types) that are easy to get up & running; String, Uint, Int, Float
 - Flexible [iteration](#iterating) of data; ascending, descending, and ranges
-- [Durable append-only file](#append-only-file) format. Similar to [Redis AOF](http://redis.io/topics/persistence)
+- [Durable append-only file](#append-only-file) format for persistence. 
 - Option to evict old items with an [expiration](#data-expiration) TTL
 - Tight codebase, under 1K loc using the `cloc` command
 - ACID semantics with locking [transactions](#transactions) that support rollbacks

buntdb.go

@@ -183,8 +183,9 @@ func (db *DB) CreateIndex(name, pattern string,
 //
 // The rect function converts a string to a rectangle. The rectangle is
 // represented by two arrays, min and max. Both arrays may have a length
-// between 1 and 4, and both arrays must match in length. A length of 1 is a
+// between 1 and 20, and both arrays must match in length. A length of 1 is a
 // one dimensional rectangle, and a length of 4 is a four dimension rectangle.
+// There is support for up to 20 dimensions.
 // The values of min must be less than the values of max at the same dimension.
 // Thus min[0] must be less-than-or-equal-to max[0].
 // The IndexRect is a default function that can be used for the rect