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<h1><a name="kanchor13"></a>Native Query Optimization</h1>
<p>Native queries will run out of the box in any environment. This optimization is turned on by default. Native queries will be converted to <a href="../soda_query.htm">SODA</a> where this is possible. This allows db4o to use indexes and optimized internal comparison algorithms. Otherwise native query may be executed by instantiating all objects, using <a href="../soda/soda_evaluations.htm">SODA evaluations</a>. Naturally performance will not be as good in this case.</p>
<H2>Optimization Theory </H2>
<p>For Native Query the <span class="PrimaryByteCode">bytecode</span> is analyzed to create an AST-like expression tree. Then the flow graph of the expression tree is analyzed and converted to a SODA query graph.</p>
<p>For example:</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IList<Pilot> result = container.Query(
delegate(Pilot pilot) { return pilot.Name == "John"; });</pre>
<div class="codesnippet-meta">NativeQueryExamples.cs: Check for equality of the name
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<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim result As IList(Of Pilot) = container.Query(Of Pilot)(AddressOf QueryJohns)</pre>
<div class="codesnippet-meta">NativeQueryExamples.vb: Check for equality of the name
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Private Shared Function QueryJohns(ByVal pilot As Pilot)
Return pilot.Name = "John"
End Function</pre>
<div class="codesnippet-meta">NativeQueryExamples.vb: Query for John
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<p>First the signature of the given <span MadCap:conditions="Primary..NET">delegate</span> is analyzed to find out the types. This is used to constrain the type in the SODA-query. Then the <span class="PrimaryByteCode">bytecode</span> of query is analyzed to find out was it does. When the operations a simple and easy to convert, it will be transformed to complete SODA query:</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof (Pilot));
query.Descend("name").Constrain("John");
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: A simple constrain on a field
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(Pilot))
query.Descend("name").Constrain("John")
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: A simple constrain on a field
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<p MadCap:conditions="Primary..NET">
<H2>Native Query Optimization</H2>
<p>Native Query optimizer for .NET requires the following libraries to work: <a href="../../../dependency_overview.htm" target="" title="" alt="" class="MCXref" xrefformat="See "{paratext}"">See "Dependency Overview"</a></p>
<ul>
<LI value="1">Db4objects.Db4o.Instrumentation.dll</LI>
<LI value="2">Db4objects.Db4o.NativeQueries.dll </LI>
<LI value="3">Mono.Cecil.dll </LI>
<LI value="4">Cecil.FlowAnalysis.dll </LI>
<LI value="5">
</LI>
</ul>
<p>These assemblies must be available in your project for successful native query optimization. </p>
<p>Current optimization supports the following constructs well:</p>
<UL>
<LI value="1">Compile-time constants.</LI>
<LI value="2">Simple member access.</LI>
<LI value="3">Primitive comparisons.</LI>
<LI value="4">Equality operator.</LI>
<LI value="5">Contains, StartsWith- and EndsWith-methods for strings.</LI>
<LI value="6">Boolean expressions.</LI>
<LI value="7">Arbitrary method calls,including property accessors, on predicate fields (without any arguments).</LI>
<LI value="8">Candidate methods composed of the above.</LI>
<LI value="9">Chained combinations of the above.</LI>
</UL>
<p>Note that the current implementation doesn't support polymorphism yet.</p>
<p>The specifics of Compact Framework platform are explained in <a href="native_query_optimization/nq_optimization_on_cf2.0.htm">NQ Optimization On CF2.0</a>. </p>
<p>An alternative optimization practice can be found in <a href="native_query_optimization/nq_build_time_optimisation.htm">Build-time Optimization For .NET</a> article.</p>
</p>
<p>For more information on native queries optimization see <a href="native_query_optimization/monitoring_optimization.htm">Monitoring Optimization</a>.</p>
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