LINQ for the Compact Framework 3.5

Db4o for .NET 3.5 ships with an optimizing LINQ provider. This provider is able to optimize the execution of a query by analyzing the LINQ expression tree emitted by the C# (or VB.NET) compiler to produce an equivalent SODA query which can be executed by db4o at full speed.The Compact Framework 3.5 however includes no support for expression trees. No expression trees, no optimizing LINQ provider. A saddening state of affairs for Compact Framework db4o users.As it turns out, expression trees are provided by the System.Linq.Expressions namespace which is not available in the standard Compact Framework 3.5 distribution.Mono to the rescueThe Mono project provides a free software implementation of the .net framework including LINQ and the System.Linq.Expressions namespace.Hypothesis: will the Compact Framework compiler emit expression trees if it sees a reference to a compatible assembly that provides a System.Linq.Expressions namespace?Yes it will. LINQ for Compact Framework seemed to be possible.There was a rema ... Read the rest of entry »

Collected Generics, Volume 1

Finally we are starting to harvest the fruits of our work on pluggable type handlers. As a first step, please welcome .NET generic collections to the exclusive club of types natively supported by db4o in the upcoming 7.6 build.In principle, .NET generic collections could already be persisted in previous versions, but there was no dedicated handling in place for them. db4o would not recognize them as collections and would simply handle them as any other object - inspect their internal layout and persist the field values found. This approach came with some pitfalls. Most notably, db4o would not recognize the collection's internal state objects as parts of a single, atomic unit - in C/S mode, concurrent updates from multiple clients against the same collections could have resulted in inconsistent internal collection state in the worst case. Furthermore, issues could arise with specific collection implementations: Dictionaries, for example, would persist hash codes alongside keys/values and could stumble when att ... Read the rest of entry »

Latest production build: 7.4.58.11547

here is a short info to resolve a race condition between our newsletter sendout and the very latest production build:

We got informed about a serious (blocker) bug with a deadlock in committed callbacks after our newsletter had already been released to marketing: COR-1377

This bug received the highest priority and it has has been fixed immediately.

A new production build with the build number 7.4.58.11547 is online in the meanwhile. If you downloaded 7.4 right after the newsletter and if you use committed callbacks or UUIDs, we recommend to check the build number you are using (call Db4o#version() / Db4oFactory#Version() ) and to download the very latest build once again if it is lower than 7.4.58.

To our knowledge this bug has been present in all 7.2 builds.