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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!--NewPage--><HTML><HEAD><TITLE>BTree (Project JXTA J2SE)</TITLE><META NAME="keywords" CONTENT="net.jxta.impl.xindice.core.filer.BTree class"><LINK REL ="stylesheet" TYPE="text/css" HREF="../../../../../../stylesheet.css" TITLE="Style"><SCRIPT type="text/javascript">function windowTitle(){ parent.document.title="BTree (Project JXTA J2SE)";}</SCRIPT></HEAD><BODY BGCOLOR="white" onload="windowTitle();"><!-- ========= START OF TOP NAVBAR ======= --><A NAME="navbar_top"><!-- --></A><A HREF="#skip-navbar_top" title="Skip navigation links"></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""><TR><TD COLSPAN=3 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3" SUMMARY=""> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/BTree.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../../index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><a href='http://www.jxta.org' target='_blank'>Project JXTA</a></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> PREV CLASS <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.BTreeFileHeader.html" title="class in net.jxta.impl.xindice.core.filer"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../../../../index.html" target="_top"><B>FRAMES</B></A> <A HREF="BTree.html" target="_top"><B>NO FRAMES</B></A> <SCRIPT type="text/javascript"> <!-- if(window==top) { document.writeln('<A HREF="../../../../../../allclasses-noframe.html"><B>All Classes</B></A>'); } //--></SCRIPT><NOSCRIPT> <A HREF="../../../../../../allclasses-noframe.html"><B>All Classes</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: <A HREF="#nested_class_summary">NESTED</A> | <A HREF="#field_summary">FIELD</A> | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: <A HREF="#field_detail">FIELD</A> | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_top"></A><!-- ========= END OF TOP NAVBAR ========= --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">net.jxta.impl.xindice.core.filer</FONT><BR>Class BTree</H2><PRE>java.lang.Object <IMG SRC="../../../../../../resources/inherit.gif" ALT="extended by"><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html" title="class in net.jxta.impl.xindice.core.filer">net.jxta.impl.xindice.core.filer.Paged</A> <IMG SRC="../../../../../../resources/inherit.gif" ALT="extended by"><B>net.jxta.impl.xindice.core.filer.BTree</B></PRE><DL><DT><B>Direct Known Subclasses:</B> <DD><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTreeFiler.html" title="class in net.jxta.impl.xindice.core.filer">BTreeFiler</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/indexer/NameIndexer.html" title="class in net.jxta.impl.xindice.core.indexer">NameIndexer</A></DD></DL><HR><DL><DT>public class <B>BTree</B><DT>extends <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html" title="class in net.jxta.impl.xindice.core.filer">Paged</A></DL><P>BTree represents a Variable Magnitude Simple-Prefix B+Tree File. A BTree is a bit flexible in that it can be used for set or map-based indexing. HashFiler uses the BTree as a set for producing RecordSet entries. The Indexers use BTree as a map for indexing entity and attribute values in Documents. <br><br> For those who don't know how a Simple-Prefix B+Tree works, the primary distinction is that instead of promoting actual keys to branch pages, when leaves are split, a shortest-possible separator is generated at the pivot. That separator is what is promoted to the parent branch (and continuing up the list). As a result, actual keys and pointers can only be found at the leaf level. This also affords the index the ability to ignore costly merging and redistribution of pages when deletions occur. Deletions only affect leaf pages in this implementation, and so it is entirely possible for a leaf page to be completely empty after all of its keys have been removed. <br><br> Also, the Variable Magnitude attribute means that the btree attempts to store as many values and pointers on one page as is possible. <br><br> This implementation supports the notion of nested roots. This means that you can create a btree where the pointers actually point to the root of a separate btree being managed in the same file.<P><P><HR><P><!-- ======== NESTED CLASS SUMMARY ======== --><A NAME="nested_class_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Nested Class Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected class</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.BTreeFileHeader.html" title="class in net.jxta.impl.xindice.core.filer">BTree.BTreeFileHeader</A></B></CODE><BR> BTreeFileHeader</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected class</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.BTreePageHeader.html" title="class in net.jxta.impl.xindice.core.filer">BTree.BTreePageHeader</A></B></CODE><BR> BTreePageHeader</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> class</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.BTreeRootInfo.html" title="class in net.jxta.impl.xindice.core.filer">BTree.BTreeRootInfo</A></B></CODE><BR> BTreeRootInfo</TD></TR></TABLE> <A NAME="nested_classes_inherited_from_class_net.jxta.impl.xindice.core.filer.Paged"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Nested classes inherited from class net.jxta.impl.xindice.core.filer.<A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html" title="class in net.jxta.impl.xindice.core.filer">Paged</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.FileHeader.html" title="class in net.jxta.impl.xindice.core.filer">Paged.FileHeader</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.Page.html" title="class in net.jxta.impl.xindice.core.filer">Paged.Page</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.PageHeader.html" title="class in net.jxta.impl.xindice.core.filer">Paged.PageHeader</A></CODE></TD></TR></TABLE> <!-- =========== FIELD SUMMARY =========== --><A NAME="field_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Field Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected static byte</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.html#BRANCH">BRANCH</A></B></CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected static byte</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.html#LEAF">LEAF</A></B></CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected static byte</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/BTree.html#STREAM">STREAM</A></B></CODE><BR> </TD></TR></TABLE> <A NAME="fields_inherited_from_class_net.jxta.impl.xindice.core.filer.Paged"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Fields inherited from class net.jxta.impl.xindice.core.filer.<A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html" title="class in net.jxta.impl.xindice.core.filer">Paged</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html#DELETED">DELETED</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html#NO_PAGE">NO_PAGE</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html#OVERFLOW">OVERFLOW</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html#sync">sync</A>, <A HREF="../../../../../../net/jxta/impl/xindice/core/filer/Paged.html#UNUSED">UNUSED</A></CODE></TD></TR></TABLE> <!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2">?? 快捷鍵說明
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