saving Btrees to a disk file and read it

Question

I want to save a Btree(not sure a binary one) in a disk file. and then read it to the memory. some Level-order traversal may be a good way for a binary Btree. but if it is not a binary one. I build up the Btree from the leafnode to the rootnode in memory. I believe that I have to define some structures in the disk file and output the tree nodes. using some extra tag to identify a node in the file? how to traversal may be the key problem here. I coudn't figure out a good way to save the nodes and the pointers. and then read it. rconstruct the tree in memory. any good ideas?. thanks a lot.

Answer 1

The usual technique for B-Trees is to ensure that the size of a node is equal to the block size of the disk, and mmap the disk file. You don't specify what programming language you're working in, so it might be as simple as a cast in C, or something more complicated such as creating flyweight objects to wrap up a java.nio.IntBuffer. Either way, much of the advantage of the B-tree is that you don't have to load it all at once, but can jump around it fairly efficiently.