For tree structures (typical binary trees), you can use the depth-first traversal and breadth-first traversal methods to browse Tree nodes. These are the most basic algorithms.
The following provides a sample code that uses deep-first traversal for tree indexes. Because the Code involves calling other methods, it is only for reference. Interested people can understand the algorithm IDEA.
| The Code is as follows: |
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Package com. databese. index. bplustree;
Import java. io. BufferedWriter;
Import java. io. File;
Import java. io. FileWriter;
Import com. databese. index. util. Const;
Import com. databese. index. util. Function;
/**
*
* Perform in-depth traversal of the entire index and generate the corresponding XML file
*
*/
Public class DFSRetrieval {
StringBuffer indexContent = new StringBuffer ();
/**
* Constructor
* @ Param indexFilePath
*/
Public DFSRetrieval (String indexFilePath)
{
This. indexRetrieval (indexFilePath );
This. write2XML ();
System. out. println ("the index is successfully converted to an XML file! ");
}
/**
* Depth-first Traversal
* @ Param indexFilePath
*/
Public void indexRetrieval (String indexFilePath)
{
String indexName = Function. getIndexName (indexFilePath );
BTree btree = BTree. openIndex (indexName );
This. indexContent. append ("<root> ");
This. nodeRetrieval (btree. index_head.root );
This. indexContent. append ("</root> ");
}
/**
* Write the index content to an external xml file.
*
*/
Public void write2XML ()
{
Try {
BufferedWriter out = new BufferedWriter (new FileWriter (new File (Const. XML_PATH )));
Out. write (this. indexContent. toString ());
Out. close ();
} Catch (Exception e)
{
E. printStackTrace ();
}
}
Public void nodeRetrieval (Node node)
{
// If it is a leaf node, all the leaf node keywords are output.
If (node instanceof LeafNode ){
For (int I = 0; I <node. used_keys; I ++)
{
This. indexContent. append ("<key> ")
. Append (node. keys [I])
. Append ("</key> ");
}
Return;
}
If (node instanceof InnerNode ){
InnerNode innerNode = (InnerNode) node;
For (int I = 0; I <innerNode. used_keys; I ++)
{
// Read the child node Information
Node childNode = innerNode. getChildNode (I );
This. indexContent. append ("<point> ");
This. nodeRetrieval (childNode );
This. indexContent. append ("</point> ");
// Read keyword Information
This. indexContent. append ("<key> ")
. Append (innerNode. keys [I])
. Append ("</key> ");
}
// Obtain the Child Information Based on the last pointer in the node
Node childNode = innerNode. getChildNode (innerNode. used_keys );
This. indexContent. append ("<point> ");
This. nodeRetrieval (childNode );
This. indexContent. append ("</point> ");
}
Return;
}
Public static void main (String [] args ){
DFSRetrieval dfsRetrieval = new DFSRetrieval ("./index/all200000.index ");
}
} |
