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An object’s OID is computed the same way git does it, SHA1(" \0"), using pgcrypto’s digest() function, and refs get compare-and-swap updates through SELECT FOR UPDATE. A libgit2 backend registers these tables as its storage layer, and if the protocol really is separable from the format, a normal git client should be able to push to and clone from a Postgres database without knowing the difference.，更多细节参见快连下载安装
A quadtree does the same thing for two-dimensional space. It takes a rectangular region and divides it into four equal quadrants: northwest, northeast, southwest, southeast. If a quadrant has too many points in it, it subdivides again and again. Each subdivision creates smaller and smaller cells where points are densely packed.