Re: Data Structure for use vs storage

> In addition to a hashtable, you can maintain a BTree index on a "primary key" column. That would considerably speed up queries like this:
> 
> (bplustree-search-range 501 1000 *my-tree*)
> 


Yes, true. But there again you are assuming an ordering relation for the key.

And to avoid problems with multiprocessing, I would instead use a purely functional Red-Black tree.

Why Red-Black? Well you’d have to ask the computer scientists that invented the OCaml standard library. I just translated what they provided there into Lisp. (IOW, I cheated…)

But purely functional has huge advantages in the face of parallel and multiple thread concurrent access. And no locks needed.



> On Feb 18, 2026, at 00:17, Dmitry Ivanov (as ystok-systema at mail dot ru) <[email protected]> wrote:
> 
> David McClain (as dbm at refined-audiometrics dot com) wrote:
> 
>> I looked at the BTree code. Interesting. But when would you use this over the built-in Hashtables of Common Lisp? In fact, with Hashtables, you don’t even need an ordering to the underlying data, just an equality comparison.
> 
> In addition to a hashtable, you can maintain a BTree index on a "primary key" column. That would considerably speed up queries like this:
> 
> (bplustree-search-range 501 1000 *my-tree*)
> 
> -- 
> Dmitry Ivanov
> lisp.ystok.ru
> 
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