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<h1>Native Query Optimization</h1><div id="TOC"><div id="TOCinner"><span class="TOCtitle">Contents</span><div class="TOCcontents"><ul><li><a href ="#Optimization Theory ">Optimization Theory </a></li><li><a href ="#NQ Optimization for .NET">NQ Optimization for .NET</a></li></ul></li></ul></div></div></div>
<P>Native Queries will run out of the box in any environment. If optimization is turned on (default) Native Queries will be converted to <a href="../object_lifecycle/querying/soda_query.html" class="wikiLink">SODA</a> where this is possible, allowing db4o to use indexes and optimized internal comparison algorithms.Otherwise Native Query may be executed by instantiating all objects, using <a href="../object_lifecycle/querying/soda_evaluations.html" class="wikiLink">SODA Evaluations</a>. Naturally performance will not be as good in this case.</P>
<a name="Optimization Theory "></a><H2>Optimization Theory </H2>
<P>For Native Query Java bytecode and .NET IL code are 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>
<span name="cs_wiki_filter" csw_filters="net">
<P>.NET: </P>
<P><code>IList<Pilot> pilots = container.Query<Pilot>(delegate(Pilot pilot) {</code></P>
<P><code> return pilot.Name.equals("Michael Schumacher")</code></P>
<P><code>&& pilot.Points == 100;</code></P>
<P><code> });</code></P>
</span>
<P>First of all the following code will be extracted:</P>
<P>query#constrain(Pilot)</P>
<P>Then a more complex analysis will be run to convert the contents of the #match method into a SODA-understandable syntax. On a simple example it is easy to see what will happen:</P>
<span name="cs_wiki_filter" csw_filters="net">
<P>.NET:</P>
<P><code>return pilot.Name.equals("Michael Schumacher") && pilot.Points == 100;</code></P>
</span>
<P>easily converts into:</P>
<P><code>CANDIDATE.name == "Michael Schumacher"</code></P>
<P><code>CANDIDATE.points == 100</code></P>
<span name="cs_wiki_filter" csw_filters="net">
<a name="NQ Optimization for .NET"></a><H2>NQ Optimization for .NET</H2>
<P>Native Query optimizer for .NET requires the following libraries to work:</P>
<UL>
<LI><SPAN id=ctl00_ctl00_bcr_topicView___TopicBody><SPAN class=net>Db4obects.Db4o.Instrumentation.dll</SPAN></SPAN></LI>
<LI><SPAN><SPAN class=net>Db4objects.Db4o.NativeQueries.dll</SPAN></SPAN></LI>
<LI><SPAN><SPAN class=net>Mono.Cecil.dll</SPAN></SPAN></LI>
<LI><SPAN><SPAN class=net>Cecil.FlowAnalysis.dll</SPAN></SPAN></LI></UL>
<P><SPAN><SPAN class=net> These assemblies must be available in your project for successful NQ optimization.<BR></P></SPAN></SPAN>
<P>The Native Query optimizer is still under development to eventually "understand" all valid C# constructs. Current optimization supports the following constructs well:</P>
<UL>
<LI>compile-time constants</LI>
<LI>simple member access</LI>
<LI>primitive comparisons</LI>
<LI>equality operator</LI>
<LI>#Contains()/#StartsWith()/#EndsWith() for Strings</LI>
<LI>boolean expressions</LI>
<LI>arbitrary method calls (including property accessors) on predicate fields (without any arguments)</LI>
<LI>candidate methods composed of the above</LI>
<LI>chained combinations of the above<BR></LI></UL>
<P>This list will constantly grow with the latest versions of db4o.</P>
<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.html" class="wikiLink">NQ Optimization On CF2.0</a>. </P>
<P>An alternative optimization practice can be found in <a href="native_query_optimization/build-time_optimization_for_.net.html" class="wikiLink">Build-time Optimization For .NET</a> article.<BR></P>
</span>
<P>For more information on NQ optimization see <a href="native_query_optimization/monitoring_optimization.html" class="wikiLink">Monitoring Optimization</a>.<BR></P></div>
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This revision (22) was last Modified 2008-04-25T19:28:42 by Tetyana.
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