[elephant-devel] Best way of getting a collection size

[Ian Eslick]

I'm not sure offhand.  Different stores will have different low-level  
access to the data structure.  Robert might be able to do this via a  
SQL query.  Not sure about Henrik's Postmodern implementation.

This probably isn't possible for the BDB data store.  You can get the  
leaf count for a BDB Btree, but not for a subtree (we multiplex  
Elephant BTrees on a single, large BDB BTree).

Perhaps we could provide a mixin class that automatically maintains  
this count on the lisp side for a user subclass of persistent- 
collection?

Ian


On Oct 2, 2007, at 10:34 AM, Mariano Montone wrote:

> Hello,
>         I would like to know which is the best way to get the size  
> of a persistent-collection (for example the number of instances of  
> some class). I haven't be able to find a method. And uploading all  
> the objects to memory to count them is not an option.
>
> Cheers, Mariano
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