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Zope Object Database: object database and persistence

Project description

The Zope Object Database provides an object-oriented database for Python that provides a high-degree of transparency. Applications can take advantage of object database features with few, if any, changes to application logic. ZODB includes features such as a plugable storage interface, rich transaction support, and undo.

ZODB

Introduction

The ZODB package provides a set of tools for using the Zope Object Database (ZODB).

Our primary development platforms are Linux and Mac OS X. The test suite should pass without error on these platforms and, hopefully, Windows, although it can take a long time on Windows – longer if you use ZoneAlarm.

Compatibility

ZODB 5 requires Python 2.7 (>= 2.7.9) or Python >= 3.3.

For developers of ZODB

Building

Bootstrap buildout, if necessary using bootstrap.py:

python bootstrap.py

Run the buildout:

bin/buildout

Testing

The ZODB checkouts are buildouts. When working from a ZODB checkout, first run the bootstrap.py script to initialize the buildout:

% python bootstrap.py

and then use the buildout script to build ZODB and gather the dependencies:

% bin/buildout

This creates a test script:

% bin/test -v

This command will run all the tests, printing a single dot for each test. When it finishes, it will print a test summary. The exact number of tests can vary depending on platform and available third-party libraries.:

Ran 1182 tests in 241.269s

OK

The test script has many more options. Use the -h or --help options to see a file list of options. The default test suite omits several tests that depend on third-party software or that take a long time to run. To run all the available tests use the --all option. Running all the tests takes much longer.:

Ran 1561 tests in 1461.557s

OK

Generating docs

cd to the doc directory and:

make html

Contributing

Almost any code change should include tests.

Any change that changes features should include documentation updates.

Maintenance scripts

Several scripts are provided with the ZODB and can help for analyzing, debugging, checking for consistency, summarizing content, reporting space used by objects, doing backups, artificial load testing, etc. Look at the ZODB/script directory for more informations.

License

ZODB is distributed under the Zope Public License, an OSI-approved open source license. Please see the LICENSE.txt file for terms and conditions.

Change History

5.1.1 (2016-11-18)

  • Fixed: ZODB.Connection.TransactionMetaData didn’t support custom data storage that some storages rely on.

5.1.0 (2016-11-17)

  • ZODB now translates transaction meta data, user and description from text to bytes before passing them to storages, and converts them back to text when retrieving them from storages in the history, undoLog and undoInfo methods.

    The IDatabase interface was updated to reflect that history, undoLog and undoInfo are available on database objects. (They were always available, but not documented in the interface.)

5.0.1 (2016-11-17)

  • Fix an AttributeError that DemoStorage could raise if it was asked to store a blob into a temporary changes before reading a blob. See issue 103.
  • Call _p_resolveConflict() even if a conflicting change doesn’t change the state. This reverts to the behaviour of 3.10.3 and older.
  • Closing a Connection now reverts its transaction_manager to None. This helps prevent errors and release resources when the transaction_manager was the (default) thread-local manager. See issue 114.
  • Many docstrings have been improved.

5.0.0 (2016-09-06)

Major internal improvements and cleanups plus:

  • Added a connection prefetch method that can be used to request that a storage prefect data an application will need:

    conn.prefetch(obj, ...)
    

    Where arguments can be objects, object ids, or iterables of objects or object ids.

    Added optional prefetch methods to the storage APIs. If a storage doesn’t support prefetch, then the connection prefetch method is a noop.

  • fstail: print the txn offset and header size, instead of only the data offset. fstail can now be used to truncate a DB at the right offset.

  • Drop support for old commit protocol. All of the build-in storages implement the new protocol. This new protocol allows storages to provide better write performance by allowing multiple commits to execute in parallel.

5.0.0b1 (2016-08-04)

  • fstail: print the txn offset and header size, instead of only the data offset. fstail can now be used to truncate a DB at the right offset.

Numerous internal cleanups, including:

  • Changed the way the root object was created. Now the root object is created using a database connection, rather than by making low-level storage calls.
  • Drop support for the old commit protocol.
  • Internal FileStorage-undo fixes that should allow undo in some cases where it didn’t work before.
  • Drop the version argument to some methods where it was the last argument and optional.

5.0.0a6 (2016-07-21)

  • Added a connection prefetch method that can be used to request that a storage prefect data an application will need:

    conn.prefetch(obj, ...)
    

    Where arguments can be objects, object ids, or iterables of objects or object ids.

    Added optional prefetch methods to the storage APIs. If a storage doesn’t support prefetch, then the connection prefetch method is a noop.

5.0.0a5 (2016-07-06)

Drop support for old commit protocol. All of the build-in storages implement the new protocol. This new protocol allows storages to provide better write performance by allowing multiple commits to execute in parallel.

5.0.0a1 (2016-06-20)

Major internal implementation changes to the Multi Version Concurrency Control (MVCC) implementation:

  • For storages that implement IMVCCStorage (RelStorage), no longer implement MVCC in ZODB.

  • For other storages, MVCC is implemented using an additional storage layer. This underlying layer works by calling loadBefore. The low-level storage load method isn’t used any more.

    This change allows server-nased storages like ZEO and NEO to be implemented more simply and cleanly.

4.4.3 (2016-08-04)

  • Internal FileStorage-undo fixes that should allow undo in some cases where it didn’t work before.
  • fstail: print the txn offset and header size, instead of only the data offset. fstail can now be used to truncate a DB at the right offset.

4.4.2 (2016-07-08)

Better support of the new commit protocol. This fixes issues with blobs and undo. See pull requests #77, #80, #83

4.4.1 (2016-07-01)

Added IMultiCommitStorage to directly represent the changes in the 4.4.0 release and to make complient storages introspectable.

4.4.0 (2016-06-30)

This release begins evolution to a more effcient commit protocol that allows storage implementations, like NEO, to support multiple transactions committing at the same time, for greater write parallelism.

This release updates IStorage:

  • The committed transaction’s ID is returned by tpc_finish, rather than being returned in response store and tpc_vote results.
  • tpc_vote is now expected to return None or a list of object ids for objects for which conflicts were resolved.

This release works with storages that implemented the older version of the storage interface, but also supports storages that implement the updated interface.

4.3.1 (2016-06-06)

  • Fixed: FileStorage loadBefore didn’t handle deleted/undone data correctly.

4.3.0 (2016-05-31)

  • Drop support for Python 2.6 and 3.2.
  • Make the zodbpickle dependency required and not conditional. This fixes various packaging issues involving pip and its wheel cache. zodbpickle was only optional under Python 2.6 so this change only impacts users of that version. See https://github.com/zopefoundation/ZODB/pull/42.
  • Add support for Python 3.5.
  • Avoid failure during cleanup of nested databases that provide MVCC on storage level (Relstorage). https://github.com/zopefoundation/ZODB/issues/45
  • Remove useless dependency to zdaemon in setup.py. Remove ZEO documentation. Both were leftovers from the time where ZEO was part of this repository.
  • Fix possible data corruption after FileStorage is truncated to roll back a transaction. https://github.com/zopefoundation/ZODB/pull/52
  • DemoStorage: add support for conflict resolution and fix history() https://github.com/zopefoundation/ZODB/pull/58
  • Fixed a test that depended on implementation-specific behavior in tpc_finish

4.2.0 (2015-06-02)

4.2.0b1 (2015-05-22)

  • Log failed conflict resolution attempts at DEBUG level. See: https://github.com/zopefoundation/ZODB/pull/29.
  • Fix command-line parsing of --verbose and --verify arguments. (The short versions, -v and -V, were parsed correctly.)
  • Add support for PyPy.
  • Fix the methods in ZODB.serialize that find object references under Python 2.7 (used in scripts like referrers, netspace, and fsrecover among others). This requires the addition of the zodbpickle dependency.
  • FileStorage: fix an edge case when disk space runs out while packing, do not leave the .pack file around. That would block any write to the to-be-packed Data.fs, because the disk would stay at 0 bytes free. See https://github.com/zopefoundation/ZODB/pull/21.

4.1.0 (2015-01-11)

  • Fix registration of custom logging level names (“BLATHER”, “TRACE”).

    We have been registering them in the wrong order since 2004. Before Python 3.4, the stdlib logging module masked the error by registering them in both directions.

  • Add support for Python 3.4.

4.0.1 (2014-07-13)

  • Fix POSKeyError during transaction.commit when after savepoint.rollback. See https://github.com/zopefoundation/ZODB/issues/16
  • Ensure that the pickler used in PyPy always has a persistent_id attribute (inst_persistent_id is not present on the pure-Python pickler). (PR #17)
  • Provide better error reporting when trying to load an object on a closed connection.

4.0.0 (2013-08-18)

Finally released.

4.0.0b3 (2013-06-11)

  • Switch to using non-backward-compatible pickles (protocol 3, without storing bytes as strings) under Python 3. Updated the magic number for file-storage files under Python3 to indicate the incompatibility.
  • Fixed: A UnicodeDecodeError could happen for non-ASCII OIDs when using bushy blob layout.

4.0.0b2 (2013-05-14)

  • Extended the filename renormalizer used for blob doctests to support the filenames used by ZEO in non-shared mode.
  • Added url parameter to setup() (PyPI says it is required).

4.0.0b1 (2013-05-10)

  • Skipped non-unit tests in setup.py test. Use the buildout to run tests requiring “layer” support.
  • Included the filename in the exception message to support debugging in case loadBlob does not find the file.
  • Added support for Python 3.2 / 3.3.

Note

ZODB 4.0.x is supported on Python 3.x for new applications only. Due to changes in the standard library’s pickle support, the Python3 support does not provide forward- or backward-compatibility at the data level with Python2. A future version of ZODB may add such support.

Applications which need migrate data from Python2 to Python3 should plan to script this migration using separte databases, e.g. via a “dump-and-reload” approach, or by providing explicit fix-ups of the pickled values as transactions are copied between storages.

4.0.0a4 (2012-12-17)

  • Enforced usage of bytes for _p_serial of persistent objects (fixes compatibility with recent persistent releases).

4.0.0a3 (2012-12-01)

  • Fixed: An elaborate test for trvial logic corrupted module state in a
    way that made other tests fail spuriously.

4.0.0a2 (2012-11-13)

Bugs Fixed

  • An unneeded left-over setting in setup.py caused installation with pip to fail.

4.0.0a1 (2012-11-07)

New Features

  • The persistent and BTrees packages are now released as separate distributions, on which ZODB now depends.
  • ZODB no longer depends on zope.event. It now uses ZODB.event, which uses zope.event if it is installed. You can override ZODB.event.notify to provide your own event handling, although zope.event is recommended.
  • BTrees allowed object keys with insane comparison. (Comparison inherited from object, which compares based on in-process address.) Now BTrees raise TypeError if an attempt is made to save a key with comparison inherited from object. (This doesn’t apply to old-style class instances.)

Bugs Fixed

  • Ensured that the export file and index file created by repozo share the same timestamp.

    https://bugs.launchpad.net/zodb/+bug/993350

  • Pinned the transaction and manuel dependencies to Python 2.5- compatible versions when installing under Python 2.5.

Note

Please see doc/HISTORY.txt for changelog entries for older versions of ZODB.

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