The Zope Object Database, ZODB, version 3.0

ZODB is the next generation of our object database architecture. It provides a number of advantages over or existing databases:

• Support for concurrency,
• Well-defined storage management interface that will allow many different storage management strategies to be used, from file storage, to RDBMS storage, to memory storage,
• More robust file storage format,
• Much better version support and integrations of versions with the transaction system. For example, it is possible to commit from one version to another, to undo version commit and abort, and to use "temporary versions" to reduce memory use when manipulating large quantities of data.
• Support for multiple databases in the same object system.
• Support for multi-process storage managers, although the standard distribution will not include any multiple process storage managers.

Note: Using ZODB 3 from Python

In ZODB 2, you could access the top-level application object with:

      import Main
      app=Main.app

You could then navigate from the top-level object by getting attributes, calling methods, etc..

In ZODB 3, you get the top-level object like this:

      import Zope
      app=Zope.app()

      ... do stuff with objects

      # and when you're done:
      app._p_jar.close()

You have to import the Zope application module, which uses ZODB 3 rather than ZODB 2. In ZODB 3, you have to get a connection to a database before you access an object. The app() function combines opening a connection and getting the top level object. When your done using the top-level object (or any objects accessible from it) you can close the database connection by calling the close method on the _p_jar attribute, which is the database connection. You don't need to close the connection if you are going to exit Python without doing any more work.

Don't forget to:

      get_transaction().commit()

If you want any changes to made to be saved.

Note: Converting ZODB 2 (aka BoboPOS) data files to ZODB 3.

The bbb.py script in utilities can be used to convert data files from ZODB 2 to ZODB 3 format:

      utilities/bbb.py -f output_file input_file

Here's a example:

       utilities/bbb.py -f var/Data.fs var/Data.bbb

        You can also convert export files from ZODB 2 by inclding the
    -x option::

       utilities/bbb.py -x -f output.zexp input.bbe

ZODB 3 and Zope Database Adapters

Most database adapters are currently likely to be problematic unless the underlying extensions and libraries:

• allow multiple simultaneous database connections,
• are thread safe,
• give up the Python global interpreter lock when making database calls.

This is only a problem when running Zope 2 with multiple threads.

ZODB 3 Futures

These are features that are lkely to wait for releases after 2.0.

• Multiple database support
• OPTIMIZATION: FileStorage will get a more efficient data structure for maintaining index information and key methods in the ZODB framework will move to C.