Writing Maintainable
Unit Tests
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NHibernate 2.0 and Cascading Deletes
April 12, 2008The first alpha version of NHibernate 2.0 has been released some time ago. Oren has put a nice overview of the new features and the bugs that are solved for this first drop. In spite the fact that they put the word 'alpha' in the version name, it is actually RTM quality!
One of the great new additions is the on-delete attribute of the key element for mapping collections.:
<set name="Permissions" inverse="true" cascade="save-update">
<key name="Authorization" on-delete="cascade"/>
<one-to-many class="Permission"/>
</set>
This particular feature solves the issue I've had with one-shot deletes on inverse collections (which I described here). Configuring it this way ensures that NHibernate relies on database-level ON CASCADE DELETE foreign key constraints. This implies that when an object with a collection of child objects is deleted, a single DELETE statement is used to remove all children at once instead of individual DELETE statements for each child object (which are called orphans at this point).
There are some things that you have to take into account here. First, this option bypasses NHibernate's optimistic locking strategy for versioned data. Second, make sure that you configure cascade="save-update" instead of cascade="all" to prevent NHibernate from performing delete cascade checks. This is important when lazy loading is enabled for the collection because it prevents that NHibernate loads one-to-many associations into memory.
I'm really excited about this new release. Kudos to the men and women who have put so much effort in building such a wonderful ORM solution!
Till next time
If you're interested in an in-person or online course that teaches you and your team how to write maintainable unit tests and get the most out of TDD practices, make sure to have a look at our trainings and workshops or contact us at info@principal-it.be.
Jan Van Ryswyck
Thank you for visiting my blog. I’m a professional software developer since Y2K. A blogger since Y2K+5. Provider of training and coaching in XP practices. Curator of the Awesome Talks list. Past organizer of the European Virtual ALT.NET meetings. Thinking and learning about all kinds of technologies since forever.
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Writing Maintainable
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About
Thank you for visiting my website. I’m a professional software developer since Y2K. A blogger since Y2K+5. Provider of training and coaching in XP practices. Curator of the Awesome Talks list. Past organizer of the European Virtual ALT.NET meetings. Thinking and learning about all kinds of technologies since forever.
Latest articles
Indirect Inputs and Outputs
April 1, 2020
State versus Behaviour Verification
March 25, 2020
Cascading Failures
March 18, 2020
The Designing versus Testing Mindset
March 12, 2020
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(+32) 496 38 00 82
info@principal-it.be