Db4o select performance?
There are two things to check Have you added the 'Db4objects. Db4o. NativeQueries'-assembly?
Without this assembly, a native query cannot be optimized Have set an index on the field which represents the Name? A index should make query a lot faster Index: cfg.Common. ObjectClass(typeof(YourObject)).
ObjectField("fieldName"). Indexed(true).
There are two things to check. Have you added the 'Db4objects. Db4o.
NativeQueries'-assembly? Without this assembly, a native query cannot be optimized. Have set an index on the field which represents the Name?
A index should make query a lot faster Index: cfg.Common. ObjectClass(typeof(YourObject)). ObjectField("fieldName").
Indexed(true).
This question is kinda old, but perhaps this is of any use: When using native queries, try to set a breakpoint on the lambda expression. If the breakpoint is actually invoked, you're in trouble because the optimization failed. To invoke the lambda, each of the objects will have to be instantiated which is very costly.
If optimization worked, the lambda expression tree will be analyzed and the actual code won't be needed, thus breakpoints won't be triggered. Also note that settings indexes on fields must be performed before opening the connection. Last, I have a test case of simple objects.
When I started without query optimization and indexing (and worse, using a server that was forced to use the GenericReflector because I failed to provide the model . Dlls), it too 600s for a three-criteria query on about 100,000 objects. Now it takes 6s for the same query on 2.5M objects so there is really a HUGE gain.
Again, db4o's API is remarkably succinct. First, the class that models a database is db4o's ObjectContainer. To put an object into a database, you merely need to pass a reference to that object to the ObjectContainer's set() method.
The db4o engine discovers the object's structure invisibly, regardless of the depth and complexity of that structure. So, in our example, not only is the Patient object stored, but its member ArrayList (weightHistory) and the WeightEntry object (within the ArrayList) are all stored as well. This characteristic—that all objects referenced by an object that is persistent are also persistent—is referred to as "persistence by reachability."
Notice that, before I opened the database, I called a pair of methods that configured the db4o engine to make the database replication capable. Specifically, I set global parameters so that any database subsequently created by the application would have UUIDs and version numbers enabled. Again, these options are going to cost us a bit in terms of performance and space consumed, so you only set them for databases to be replicated.
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