<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="2" MadCap:lastHeight="120" MadCap:lastWidth="624" MadCap:disableMasterStylesheet="true" MadCap:tocPath="Configuration|Common Configuration" MadCap:InPreviewMode="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" MadCap:PathToHelpSystem="../../../" MadCap:HelpSystemFileName="index.xml" MadCap:SearchType="Stem"> <head><title>B-Tree Node Size</title> <script type="text/javascript">/* <![CDATA[ */ window.onload = function(){ var pathToFlash = $('html').attr('MadCap:PathToHelpSystem') + 'Content/Resources/Code/ZeroClipboard.swf'; ZeroClipboard.setMoviePath(pathToFlash); function bindToClipBord(element,content){ var clip = new ZeroClipboard.Client(); clip.setText(content); clip.glue(element); }; if(location.protocol==='file:'){ $('.copylink-marker').remove(); } else{ $('.copylink-marker').each(function(){ var text = $(this).parent().parent().children('.prettyprint').html(); $(this).hover(function(){ bindToClipBord(this,text); }, function(){}); }); } prettyPrint(); }; /* ]]> */</script> <link href="../../SkinSupport/MadCap.css" rel="stylesheet" /> <link href="../../Resources/Stylesheets/OnlineStyle.css" rel="stylesheet" /> <script src="../../Resources/Code/prettify.js"> </script> <script src="../../Resources/Code/lang-vb.js"> </script> <script src="../../Resources/Code/jquery.min.js"> </script> <script src="../../Resources/Code/ZeroClipboard.js"> </script> <script src="../../SkinSupport/MadCapAll.js" type="text/javascript"> </script> </head> <body> <p class="MCWebHelpFramesetLink" style="display: none;"><a href="../../../index_CSH.html#configuration/common/btree_node_size.htm" style="">Open topic with navigation</a> </p> <div class="MCBreadcrumbsBox"><span class="MCBreadcrumbsPrefix">You are here: </span><a class="MCBreadcrumbsLink" href="../../configuration.htm">Configuration</a><span class="MCBreadcrumbsDivider"> > </span><a class="MCBreadcrumbsLink" href="../common_configuration.htm">Common Configuration</a><span class="MCBreadcrumbsDivider"> > </span><span class="MCBreadcrumbs">B-Tree Node Size</span> </div> <p> <script type="text/javascript">/*<![CDATA[*/document.write('<a href="' + location.href +'">'); document.write("Direct Link"); document.write('</a>');/*]]>*/</script> </p> <p> </p> <h1>B-Tree Node Size</h1> <p>db4o uses B-tree indexes for increased query performance and reduced memory consumption. B-trees are used for <a href="../objectfield_configuration.htm#Adding">field-index</a>, <a href="../objectclass/diable_class_index.htm">class-index</a> and for the <a href="../id_system.htm">id-system</a>. B-trees are optimized for scenarios where a part of the data is on secondary storage such as a hard disk, since disk accesses is extremely expensive. B-trees minimize the number of disk accesses required. You find more information <a href="http://en.wikipedia.org/wiki/B-tree">about B-trees on the internet</a>.</p> <p>You can tune the B-trees by configuring the size of a node. Larger node sizes require less disk access, since a node is read on one read-operation. However it consumes more memory to keep the larger nodes available. Also larger nodes take longer to write back to disk. You need to tune the B-tree node size according to your application requirements. When benchmarking the settings, use large data sets. The influence of B-trees is more significant for larger dabases with 100'000 and more objects.</p> <div class="codesnippet" MadCap:conditions="Primary.c#"> <pre class="prettyprint" xml:space="preserve">IEmbeddedConfiguration configuration = Db4oEmbedded.NewConfiguration(); configuration.Common.BTreeNodeSize = 256;</pre> <div class="codesnippet-meta">CommonConfigurationExamples.cs: Change B-tree node size <div class="codedownload"><a href="../../CodeExamples/configuration/common/Example-configuration-common-csharp.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div> </div> <div class="codesnippet" MadCap:conditions="Primary.VB.NET"> <pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim configuration As IEmbeddedConfiguration = Db4oEmbedded.NewConfiguration() configuration.Common.BTreeNodeSize = 256</pre> <div class="codesnippet-meta">CommonConfigurationExamples.vb: Change B-tree node size <div class="codedownload"><a href="../../CodeExamples/configuration/common/Example-configuration-common-vb.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div> </div> <script type="text/javascript" src="../../SkinSupport/MadCapBodyEnd.js"> </script> </body> </html>