Community News

Tips on indexing and query optimization

German Viscuso — Sun, 04 Jan 2009 16:49:00 GMT

This blog post shows some indexing basics and performance tips by Arne Claassen. Among other things Arne shows you which assemblies to include to make sure your native queries can be optimized. Thanks Arne!

db4o v7.4 working on Mono

German Viscuso — Sun, 04 Jan 2009 15:01:00 GMT

Arne Claassen has been playing with db4o under Mono and came up with a DLL for db4o v7.4 that works beautifully across .NET and Mono from a single build. See his blog post here.

Using db4o for unit test results verification

German Viscuso — Sat, 03 Jan 2009 21:14:00 GMT

The author of Nails and Hammers shows how to use the TestSpy pattern (described in Gerard Meszaros' xUnit Test Patterns) in combination with db4o. TestSpy is a class that can be ‘injected' in a tested class in order to instrument and capture its behaviour. In this blog post TestSpy is used to persist objects that were being created in the tested method to be verified at a later stage.

"I had wide number of choices how to implement the persistence - using a file, a regular sql database, embedded database like HSQLDB or H2. I really wanted something simple, no extra server administration, table creation or O/R mapping definition. I wanted to store and retrieve objects, so I decided to give it a try with an embedded object-oriented database. I chose db4o for no particular reason except that it seems to be pretty well established as a product and is coming with an open source license (GPL, though)" says the author.

"Despite having not much of former exposure to db4o, it turned out pretty quick and simple. I followed the tutorial and I had the whole testing up and running in about 30 minutes".

You can read the blog post here.

Towards Native Queries

German Viscuso — Sat, 27 Dec 2008 16:06:00 GMT

I just saw Gavin's recent blog post where he announces: "The public draft of the JPA 2.0 specification is already out and includes a much-awaited feature: an API that lets you create queries by calling methods of Java objects".

It seems that the mapping persistence community at least agrees on the advantage of being able to refactor your queries. Then Gavin continues:

"There's several reasons to prefer the API-based approach:

It's easier to build queries dynamically, to handle cases where the query structure varies depending upon runtime conditions.
Since the query is parsed by the Java compiler, no special tooling is needed in order to get syntactic validation, autocompletion and refactoring support.

[...] There's two major problems with criteria query APIs in the Java language:

The queries are more verbose and less readable.
Attributes must be specified using string-based names."

Sounds like our SODA.

This is precisely why I really like db4o Native Queries (available since db4o v5 released on Nov 2005) and LINQ support on the .NET version. Native Queries are fully checked at compile time, they can be written using IDE autocompletion and they can be automatically refactored by the IDE. In spite of any implementation detail with the db4o version (such as query optimization) and whether the future of NQs will look more like LINQ (even on the Java side) than the current db4o implementation I sincerely think that this is the way to go, no strings just objects.

In any case congrats to the Hibernate/JPA community for another step in the right direction (though IMHO there's still a long way to go)

ODBMS.ORG TechView Product Reports Published

German Viscuso — Mon, 22 Dec 2008 22:30:00 GMT

ODBMS.ORG, a vendor-independent non-profit group of high-profile software experts lead by Prof. Roberto Zicari, today announced the exclusive publication of four in depth technical reports called TechView, featuring four leading object database products:

db4o
Objectivity/DB
ObjectStore
Versant Object Database

"Most of the time it is difficult to gather good technical information on products, without marketing or sales hype." says Prof. Zicari, Editor of ODBMS.ORG. "I therefore decided to create a series of product reports on some of the leading Object Database Systems around. For that, I have prepared 23 questions which I sent to four vendors: db4objects, Objectivity,Inc., Progress Software Corporation; and Versant Corporation.
I asked them detailed information on their products,such as: Support of Programming Languages, Queries, Data Modeling,Integration with relational data, Transactions,Persistence,Storage, Architecture,Applications, and Performance.

The result are four TechView Product Reports which contain detailed useful information on the respective products. I hope these will be useful resources for developers and architects alike", says Zicari.

The four TechView reports are available for free download: http://www.odbms.org/vendors.html
The full text of this news can be downloaded at: http://www.odbms.org/about_news_20081216.html

Follow db4o on Twitter!

German Viscuso — Wed, 17 Dec 2008 21:13:00 GMT

db4objects is now broadcasting news and updates on Twitter! =D

db4o with System.Transactions.TransactionScope

German Viscuso — Thu, 11 Dec 2008 10:54:00 GMT

Really interesting post by Jason Jarrett where he shows how to support System.Transactions on .NET with db4o. In the example Jason uses a class (Db4oEnlist.cs) that manages the enlistment of a transaction which he places as a private nested class inside the ObjectRepository<T>.

"We first create an instance of the Db4OEnlist class with the current container. This class implements the IEnlistmentNotification interface and knows how to commit/rollback/etc on the object database. We then use the private helper method Enlist() giving it the Db4OEnlist instance. This helper method enlists the sequence in any existing transactions returning if it enlisted in a transaction or not [...] If we aren't in a transaction we commit the action right away, however if we are in the transaction we let the .net System.Transaction framework take care of committing the transaction"

Check it out here (thanks Jason, great stuff!)

db4o gains support of Versant Corporation, the leading commercial ODBMS company

German Viscuso — Fri, 05 Dec 2008 00:31:00 GMT

Today it's an exciting day for db4o! Versant Corporation (Nasdaq: VSNT), the leading commercial ODBMS company and provider of specialized data management software, acquired the db4objects' database business of privately-held Servo Software, Inc. (formerly db4objects, Inc.), including db4objects' database software db4o. The db4o team (including db4objects' founder and CTO Carl Rosenberger) will join Versant and continue to support the db4objects community at large (note that there will be no disruption on db4o's present operations).

"After many years of growth in community, customer base and revenue, it is time for db4o to get to the next level", said Carl Rosenberger, founder and CTO of db4objects. "The transaction with Versant should be beneficial for our developers worldwide and our customers, and I look forward to working with all of them in this new, expanded, framework."

We would like to welcome Robert Greene, V.P. Product Strategy for Versant, who will be taking a lead in fostering the db4o community and their product vision on a going forward basis. “The db4o community has done an outstanding job of delivering a top quality object database solution to the embedded software market”, said Robert, “In the process, it has demonstrated to the entire software industry the value that object database technology adds to the software developer’s toolkit. Versant looks forward to continuing the support of the db4o open source community, helping to build long-term value for object-oriented developers.”

We thank the db4o community for the constant support and we hope you can join us in taking db4o to the next level!!!

German Viscuso
db4objects community manager

For more information please check these announcements:

http://www.versant.com/en_US/news_events/pressreleases/pressreleases_2008/earnings_release_FY2008.html/0
http://getservo.com/open/Press.aspx

Abstracting Data Access: db4o example

German Viscuso — Thu, 27 Nov 2008 02:22:00 GMT

I just run into a nice blog post by Nail Martin ("Prototyping : New wine, old skins") where he shows how to abstract data access with db4o as the underlying persistence engine (Nail is a big fan of repositories and finders, updaters and basically any technique to abstract data access and easily Mock the data layer).

Source code is included (C#) and a brief explanation on how to inject the repository against the IoC framework Unity.

We look forward for Nail's follow up blog post!

JavaFX db4o example

German Viscuso — Wed, 19 Nov 2008 04:32:00 GMT

Jos Koenen just reported that an example of db4o underJavaFX is working just fine (you might also want to check the code in his previous post here).

Don't miss this opportunity to check JavaFX persistence with db4o (source code included). Although this is a basic example you might want to contribute more advanced examples based on this one to the thread.

Thanks Jos!

db4o with IOC (Inversion of Control)

German Viscuso — Mon, 17 Nov 2008 09:22:00 GMT

In part 3 of his IOC Containers series of blog posts (part 1, part 2), Jared shows us how to use db4o (introducing a DB4OSingleServiceProvider) to transparently persist objects and use them between application instances or other systems using IOC. Source code included =)

The OMG is hosting an Object Database Standard Definition Scope meeting in Santa Clara

German Viscuso — Mon, 17 Nov 2008 09:02:00 GMT

Mike Card just announced (via Roberto Zicari's blog) that the OMG is hosting an Object Database Standard Definition Scope meeting in Santa Clara, CA at the Hyatt Regency on Tuesday afternoon, December 9th.

The agenda for this meeting will be as follows:

1300-1310 Welcome and introductory comments (Mike Card)
1310-1330 Review of scoping consensus thus far and db4o comments from last meeting (Mike Card)
1330-1630 Discussion of scope areas to be included or excluded (all participants)
1630-1700 Wrap-up and discussion of next steps (Mike Card)

And I'm glad to see that Mike says "We got some excellent feedback from db4o at our last meeting on these topics and we would like input from other vendors as well."

Let's hope other vendors join this effort (IMHO it's worth it!)

The Prizes for the db4o Powershell Provider Challenge

German Viscuso — Sat, 08 Nov 2008 19:37:00 GMT

The db4o Powershell Provider Challenge is still on! Check on these goodies:

The hosts at Powerscripting.net will be giving away a copy of PrimalScript Enterprise which has a retail value of $379. Note that PowerShellpeople like to hang out on #powershell @ FreeNode IRC network, the NNTPnewsgroup microsoft.public.windows.powershell, and last but not least,the forums at PowerShellCommunity.org . If you feel you need PowerShell help to take on this challenge, there are plenty of resources.

db4objects will also let the winner choose one item from our gift shop (http://www.cafepress.com/db4o/) or get the db4o book (http://www.amazon.com/Definitive-Guide-db4o-Stefan-Edlich/dp/1590596560)

Come and join the challenge (it's also great fun!) =)

db4o Powershell Provider Challenge - with prizes

German Viscuso — Sun, 02 Nov 2008 21:31:00 GMT

There is a challenge going on at the PowerShell Podcast (http://www.powerscripting.net) in Episode 46 (the current episode as of this writing) for anyone who can get db4o working with Microsoft Powershell. The guys hosting the podcast are giving away a prize to anyone who can accomplish the task.

For those who are not familiar with Powershell, it is the new Microsoft command line/scripting language. It works with an object pipeline instead of text strings like bash or cmd, and has full access to the dotnet framework, com, and wmi. It has also been made a part of the common engineering criteria for all Microsoft products, so it will be THE non-gui admin interface for Microsoft products for the forseeable future.

Check out the podcast, look at powershell, and if you can code, see if you can win fame and free stuff!

Thanks dschoeck for reporting!

Everybody agrees that such a project would be really cool!! I highly recommend that you check the podcast (the db4o challenge part is right in the end).

This is what the hosts say about the challenge in the Episode 47 page:

"Don’t forget our challenge from last week. If you submit a solution, we’ll feature it on the show and the website, and you’ll get a little something for your trouble. :) Here is the email from Dale which we forgot to put in last week’s show notes:"

“While trying to find a solution to a problem that popped up at work, I stumbled upon an open-source dotnet object-oriented database called Db4o. It is intended to be used as an embedded database in programs where some persistent storage is needed, but instead of storing data in related tables, it stores objects.

I’ve tried to access the functions via reflection, but I am just learning Powershell and I don’t know if this is the right technique. I haven’t gotten very far.
I was wondering if you or someone else who listens to the show could take a look at it, and see if it can be useful as an object store in powershell scripts.”

db4o and Jython (Part 2)

German Viscuso — Sat, 01 Nov 2008 07:59:00 GMT

Here's a follow up series of blog posts about db4o and Jython by Jim Cassidy: "Jython Goodness with db4o", "Jython Formula One Tutorial" and "Jython Formula One Tutorial, Part2". The last two entries are a mirror of our Formula 1 tutorial but for Jython.

And don't miss the latest entry: "Pythonic DB4O"

Thanks Jim!