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    <h1>Architecture of the file</h1> <p>Well, it's pages (= blocks). The pages should have a multiple of the page size of the underlying storage, so probably 1kb or 8kb blocks. Each block has a number and can be references this way.</p> <p>Directory pages store the bounding boxes of the children and their page numbers.</p> <p>Child pages store the actual data objects.</p> <h1>Managing the tree</h1> <p>Well, in theory: whenever you modify a page in memory, you write the changes to disk. That's it.</p> <p>In practise, you might want to use a cache for performance, and you might want to have transactions for keeping your tree consistent in case of an application crash.</p> <p>On both of these things you can find a lot of literature in the field of RDBMS architecture.</p> <p>A key benefit of the R*-tree is that it is a regular page-oriented tree as you would have them in database systems all over the place. If you have a good on disk B+-tree implementation, you can <em>reuse most of your code</em> for the R*-tree.</p> <h1>How to get started</h1> <p>To get started, you need to get used to disk-based data indexing, as it is done in classic RDBMS. I'd suggest starting with an <strong>on disk</strong> B-tree or B+-tree. Do allow deletions, because you need to think about managing deleted pages and all this.</p> <p>Once you figured out the B-Tree on disk (and maybe spend some time on optimizing it!), doing an on-disk R-tree should be fairly obvious.</p> <p>I havn't looked at the code, but this might be a good starting point: <a href="http://www.die-schoens.de/prg/" rel="nofollow noreferrer">http://www.die-schoens.de/prg/</a> or some of the others linked in <a href="https://stackoverflow.com/questions/1720738/looking-for-a-disk-based-b-tree-implementation-in-c-or-c">Looking for a disk-based B+ tree implementation in C++ or C</a></p>
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    1. POPersistent (Disk Based) R-Tree (or R* Tree)
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    1. COThanks for your answer. But now I am totally lost! Is there any step by step reference for understanding how one would actually do that? I have downloaded and read many R(*) Tree implementations in Java and some in C and C++ but I did not understand a line! I am sure that I am in a very wrong view (and never before had done something like it).
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      1. USKaveh Shahbazian
    2. COThere is more than one way to it. And it's **just not that simple**. You need to manage empty pages which you will get after performing deletions, for example. Maybe you should start with implementing a B+-tree *on disk*. Do *not* start with an in-memory implementation. Work on disk from the very beginning.
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    3. COUnfortunately I have started with an in-memory R-Tree which I like much: built by bulk insert very fast (12 sec on my machine for 2`100`000 entries) and blazing fast search speed (under 1 micro sec) and I use this in production. Maybe that rotted my mind completely because I do not understand these codes at all! I have done what you said before and started from a B-Tree but that did not help neither! I can not factor out the idea of "STORAGE" from rest of the code :(
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