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POWhy are my NHibernate queries so slow?
 

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  1. POWhy are my NHibernate queries so slow?
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    <p>I'm building an ASP web forms app with Fluent NHibernate v2.0.50727 to SQL server backend.</p> <p>For some reason querying tables with small data (~14 rows) takes seconds.</p> <p>The maps are all simple: <code>Id(x =&gt; x.Id)</code> and <code>Map(x =&gt; x.Name)</code>. CertificateGroup also Map()'s <code>Color</code> and <code>Rank</code>.</p> <p>I've isolated the nhibernate code for testing:(this is not representative of my application but is simplified and isolated for SO)</p> <pre><code>protected void Page_Load(object sender, EventArgs e) { var config = Fluently.Configure() .Database(MsSqlConfiguration.MsSql2008.ConnectionString("...")) .Mappings(m =&gt; m.FluentMappings.AddFromAssemblyOf&lt;PersonMap&gt;()) .BuildConfiguration(); var factory = config.BuildSessionFactory(); using (var session = factory.OpenSession()) { using (var transaction = session.BeginTransaction()) { var departments = session.QueryOver&lt;DepartmentModel&gt;().List(); // these all take seconds to execute - this has 14 results var jobs = session.QueryOver&lt;JobModel&gt;().List(); // 113 results var certificates = session.QueryOver&lt;CertificateModel&gt;().List(); //this one about 4 seconds for 210 results var groups = session.QueryOver&lt;CertificateGroupModel&gt;().List(); var association = new CertificateAssociationModel { Department = departments.First(), Job = jobs.First(), Certificate = certificates.First(), Group = groups.First() }; session.SaveOrUpdate(association); transaction.Commit(); } } } </code></pre> <p>I swapped nhibernate for entity framework and ran the above code and the fetches were instant.</p> <p>Any help appreciated.</p> <p>EDIT:</p> <p>Here are the mappings (as I explained above): For Department, Job and Certificate:</p> <pre><code>public class DepartmentMap : ClassMap&lt;DepartmentModel&gt; { public DepartmentMap() { Table("tblDepartment"); Id(x =&gt; x.Id); Map(x =&gt; x.Name); } } </code></pre> <p><code>CertificateGroupModel</code> also has <code>Map(x =&gt; x.Rank);</code> <code>Map(x =&gt; x.Color);</code></p> <p>Entity classes are all the same:</p> <pre><code>public class CertificateModel { public virtual Int32 Id { get; protected set; } public virtual String Name { get; set; } } </code></pre> <p>Except CertificateGroupModel which also has:</p> <pre><code>public virtual String Color { get; set; } public virtual Int32 Rank { get; set; } </code></pre> <p>Here are my NHiberate profiler results:</p> <pre><code> -- statement #1 begin transaction with isolation level: Unspecified -- statement #2 SELECT this_.Id as Id4_0_, this_.Name as Name4_0_ FROM tblDepartment this_ -- statement #3 SELECT this_.Id as Id5_0_, this_.Type as Type5_0_ FROM tblJobTitles this_ -- statement #4 SELECT this_.Id as Id2_0_, this_.Name as Name2_0_ FROM tblCertificate this_ -- statement #5 SELECT this_.Id as Id1_0_, this_.Name as Name1_0_, this_.Rank as Rank1_0_, this_.Color as Color1_0_ FROM tbl_certificate_groups this_ -- statement #6 INSERT INTO lnk_certificate_associations (Certificate_id, Department_id, Job_id, Group_id) VALUES (1 /* @p0 */, 1 /* @p1 */, 1 /* @p2 */, 1 /* @p3 */); select SCOPE_IDENTITY() -- statement #7 commit transaction </code></pre> <p><a href="http://i.snag.gy/bTKHm.jpg" rel="nofollow noreferrer">nhibprofile http://i.snag.gy/bTKHm.jpg</a></p> <p>IL code generated:</p> <pre><code> var departments = session.QueryOver&lt;DepartmentModel&gt;().List(); IL_008F: ldloc.2 /* session */ IL_0090: callvirt instance NHibernate.IQueryOver`2&lt;!!0, !!0&gt; NHibernate.ISession::QueryOver&lt;Core.Domain.Model.DepartmentModel&gt;() IL_0095: callvirt instance [mscorlib]System.Collections.Generic.IList`1&lt;!0&gt; NHibernate.IQueryOver`1&lt;Core.Domain.Model.DepartmentModel&gt;::List() IL_009A: stloc.s departments </code></pre>
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    1. USEdward Mulraney
    1. USEdward Mulraney
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      1. POWhy are my NHibernate queries so slow?
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    1. COI don't see anything out of the ordinary here, maybe save for creating the `ISessionFactory` on each page load; it should only be done once. Other than that it should run just as good as EF, the generated SQL speaks for itself, there's nothing special there.
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      1. POWhy are my NHibernate queries so slow?
      1. USPatryk Ćwiek
    2. CONo, I have just isolated the problem code for testing/solving. There is no slowness in creating the factory. The issue is with the querying. Obviously in my application I reuse the session factory.
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      1. POWhy are my NHibernate queries so slow?
      1. USEdward Mulraney
    3. COThe generated SQL is indeed correct. I have to wait seconds for `session.QueryOver<DepartmentModel>().List();` etc to execute. I can't understand why it would take seconds.
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      1. POWhy are my NHibernate queries so slow?
      1. USEdward Mulraney
 

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