[ZODB-Dev] Re: [Dev] ZODB is not a Storage Technology (Re: other formats )

Steve Alexander steve at cat-box.net
Mon Nov 11 00:20:55 PST 2002

>    particular data-types:
>        PersistentDict, PersistentList:
>            """Dictionary and List types which track their changes
>            Basically allow you to use them as lists/dicts without
>            needing to spend code tracking changes yourself.  These
>            items, however, re-store the entire list/dict on each
>            save, so see BTree for large dicts.
>            """
>        BTrees:
>            """BTree implementation using individually persistent nodes
>            Allows large dictionaries to be stored so that only a small
>            sub-set of the dictionary needs to be re-stored on 
> modifications
>            """

Note that a BTree is fundamentally different than a dictionary.

A dictionary uses hash values and equality to compare its keys.
A BTree uses a comparison operator to order its keys.

Steve Alexander

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