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Editorial Team
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Asked: 2026-05-13T19:30:11+00:00

On outer join fetching , the Nhibernate documentation says: If your database supports ANSI

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On outer join fetching, the Nhibernate documentation says:

If your database supports ANSI or
Oracle style outer joins, outer join
fetching might increase performance by
limiting the number of round trips to
and from the database (at the cost of
possibly more work performed by the
database itself). Outer join fetching
allows a graph of objects connected by
many-to-one, one-to-many or one-to-one
associations to be retrieved in a
single SQL SELECT.

I’m trying to decide if I should use outer join fetching in my current project (which uses NHibernate). To that end I’m going to be testing load times with and without outer join fetching. But I would like to know if it’s a good or bad strategy on the whole when using Sql Server 2008.

Is it generally better to use outer join fetching than not with Sql Server 2008?

How does one determine whether to use it or not? (other than through performance testing and query profiling)

Thanks

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1 Answer

  1. Editorial Team

    Weird question.
    Use outer join fetching if necessary; certain queries will require outer join fetching on some entities. Other queries won’t. So, if you do not need it, don’t fetch eagerly using outer joins.
    You can specify the type of fetching for each association when you use the ICriteria API.

    It’s all a matter of optimization, which can be done afterwards. I mean: suppose you have an object graph, where certain parts are retrieved via lazy loading, and after testing, if it seems that lazy loading affects performance in a negative way for that specific object graph, check if you could gain something by using eager loading (via outer join fetching f.i.).

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