Visit the new documentation for updated content. DB4O. Table of contents. 1 Info; 2 The Basic Principle of db4o; 3 Downloads; 4 Current Status. This tutorial was written to get you started with db4o as quickly as possible. Before you The API documentation for db4o is supplied as a compiled Help file . db4o provides sources of documentation: tutorial, reference documentation, API documenation, online paircasts and.

Author: Samurr Dar
Country: Burundi
Language: English (Spanish)
Genre: Environment
Published (Last): 12 September 2008
Pages: 135
PDF File Size: 4.54 Mb
ePub File Size: 16.85 Mb
ISBN: 227-7-45296-314-6
Downloads: 38360
Price: Free* [*Free Regsitration Required]
Uploader: Grogor

Once that’s all done, I call docu,entation on the db4o database and check to see if the ObjectSet returned contains any objects. We said earlier that when calling Store to update an object graph, that db4o will not by default descend into child objects to detect changes to the graph. Just one line of code is all it takes.

And for those situations where db4o’s native query facility fails to meet the need, the SODA API which originally appeared as a standalone query system for any object system, and still lives on SourceForge allows you to tune the query down to its tiniest detail, at the expense of simplicity.

Queries, updates, and identity

Special cases can be handled through writing custom type handlers. The community of db4o registered members grew to over 60, members. Views Read Edit View history. However, this mode has limitations. An iterator is created against the best index found. Maybe Brian was added a couple of years ago, before he turned Matching values will be the same object instance as the supplied value.


Higher values should be used to debug UpdateDepth-related issues only. Accessing the Count or Length properties will cause full evaluation. Over a million developers have joined DZone. The community votes for most important features and most critical bugs is taken into consideration when defining the road map and weekly iteration plans. You can also documehtation the db. NQ can do all documentaion because they are expressed as native.

If a field in the prototype is “null,” then that value matches against any documemtation in the data store; otherwise, the values must match exactly. MaxValue will cause db4o to descend as deeply as possible to look for changes. This documentatin is part of in the series: Calling Store with 2 User objects both with an ID of “jack” will result in documentatiin separate instances. Documentatin db4o requires only the. Because db4o uses the native object or referential identity, it’s better to open the database or connection when your application begins, do all your work, then close the database when your program is shutting down.

Comments Sign in or register to add and subscribe to comments. A similar effect would occur if the persons. Queries, updates, and identity. Practically speaking, this means you have to be more careful about objects-in-memory-versus-objects-in-storage when working with an object database.

It was developed, commercially licensed and supported by Actian. While a db4o database file is open, it is locked and cannot be accessed by another application at the same time.

The busy Java developer’s guide to db4o: Queries, updates, and identity

Clearly the first option above is only viable for the most trivial of databases because it puts an obvious upper-bound on the size of the database that you can practically use. The documntation option pollutes the simplicity of the QBE approach and leads to monstrosities like the one shown in Listing A properly tuned activation depth is the best way to optimize retrieval of data from a db4o database.


If the bytecode is easy enough to understand, db4o will turn that query into a SODA query for efficiency, in which case there is no need to instantiate all the objects to pass into the match method.

Production version is meant to be used in production environment and includes features that have been already evaluated and proven by time. Information storage and retrieval has been nearly synonymous with RDBMS for about a decade now, but recently that has begun to change.

Db4o – Wikipedia

A full description of Class-specific and field-specific configuration settings can be found in the db4o reference documentation.

One of its main goals is to provide an easy and native interface to persistence for object oriented programming languages. About this series Information storage and retrieval has been nearly synonymous with RDBMS for about a decade now, but recently that has begun to change.