rez - Revision Database Library

This is a `simple' revision-capable database for java. It uses BerkeleyDB JE Direct Persistent Layer (DPL) for storage.

This is the interim result of a very slow-burning long term personal project which stretches back over a decade. It has been through C and Java, and multiple iterations of refinement and simplification.

By design this software is intended for use by individuals and for embedded use. It has no business or `enterprise' related features. Distributed operation was not considered as part of the design.

Details of Note

The revision model supported is something of a amalgamation of cvs and subversion features. I think it takes the best of both worlds - which means more cvs and less subversion.

• Revision tree is global. The revision tree is shared across all versioned objects. This makes certain operations much faster.
• Branches are revision branches. Branches are implemented as forks in the global revision tree and not as `cheap copies'. I find this much easier to understand. Cheap copies and/or file aliases may be possible within the defined schema but will never be supported.
• Tags are zero-cost. Tags are merely text labels applied to a specific revision number.
• Branches are almost zero-cost. Branches cost nothing extra to commit to and add a small potential cost to all retrievals.
• Updates are transactional. Additionally multiple updates to data and meta-data can be combined into a single revision update.
• Compact storage. DEZ1 is used to encode compact reverse deltas for binary data.
• Objects can be renamed. Object metadata such as the name is also versioned. Different objects of the same name may reside on separate branches as expected.
• Efficient retrieval. Retrieval should (should?) be efficient in terms of computational resources. The branch membership test is cheap and requires only tiny in-memory table walks.
• Keywords & metadata. Objects can be retrieved by indexed keywords. Objects can have additional application meta-data attached.
• Small. Outside of quite a bit of scaffolding to use Berkeley DB JE and to support Java8 Stream interfaces, there is very little code required.

For further background on the internals of this software refer to my `Java Versioned Database' article.

The API is still expermental but currently utilises Java8 Stream interfaces, thus Java8 is required to build and use.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Downloads

• rez-0.1.tar.gz source code.

  28/3/2015: Initial public release.

  • Core functionality should work.
  • Merges are up to the application.
  • Meta-data api still in flux - currently all updates are write-once.
  • Authentication mechanism is still work in progress.

Links

• rez homepage - should be this page;
• dez homepage - a build dependency.

Contact

notzed on various mail servers, primarily gmail.com.