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POBest way to delete all rows in a table using NHibernate?
 

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  1. POBest way to delete all rows in a table using NHibernate?
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    <p>To keep my integration tests independent I remove all old data and insert new test data before each test. Is there a better way of doing this than simply querying for all entities and deleting them one by one?</p> <p>I have considered writing a stored proc that runs "delete from <em>tablename</em>;" for each table that is to be cleared. That ought to quite a bit faster, but it would be nice to do it without doing SQL queries or calling SPs via NH.</p> <p>I'm using vanilla NHibernate and Linq to NHibernate. I beleive Castle Active Record has something like Foo.DeleteAll(), but I don't want to use Active Record for this project.</p> <p>Any ideas?</p> <p>Thanks /Erik</p> <p><strong>UPDATE:</strong></p> <p>Since this question was asked and answered, progress has been made by the NHibernate team. As Ayende explains in <a href="http://ayende.com/Blog/archive/2009/05/28/nhibernate-ndash-executable-dml.aspx" rel="noreferrer">this blog post</a>, you can now execute DML queries directly, without NHibernate having to fetch any entities.</p> <p>To delete all Foo objects you could do like this:</p> <pre><code>using (ISession session = ...) using (ITransaction transaction = session.BeginTransaction()) { session.CreateQuery("delete Foo f").ExecuteUpdate(); transaction.Commit(); } </code></pre> <p>This query would generate the following SQL:</p> <pre><code>delete from Foo </code></pre> <p>which aught to be significantly faster than fetching the entities first and then deleting them. Be careful though, since queries like these do not affect the level 1 cache.</p>
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    1. USErik Öjebo
    1. USErik Öjebo
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    1. COIf you are using SQL Server it is MUCH more efficient to execute `TRUNCATE TABLE foo;` as that is a minimally logged operation. Executing `DELETE FROM foo;` logs all the deletes for recovery purposes; on large tables this requires significant disk/time.
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      1. POBest way to delete all rows in a table using NHibernate?
      1. USMatt Rogish
    2. COTRUNCATE TABLE is almost never available when there are foreign keys involved.
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      1. POBest way to delete all rows in a table using NHibernate?
      1. USJeremy Holovacs
 

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