Lucene索引的删除和更新

删除和更新和新增一样，也是通过IndexWriter 对象来操作的，IndexWrite对象的deleteDocuments ()方法用于实现索引的删除，updateDocument()方法用于实现索引的更新。

删除Lucene索引

删除索引的代码如下，该示例实现了根据Term来删除单个或多个Document,删除title中包含关键词“美国”的文档：

import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import tup.lucene.ik.IKAnalyzer6x;
public class DeleteIndex {
    public static void main(String[] args) {
    // 删除title中含有关键词“美国”的文档
    deleteDoc("title", "美国");
}
public static void deleteDoc(String field, String key) {
    Analyzer analyzer = new IKAnalyzer6x();
    IndexWriterConfig icw = new IndexWriterConfig(analyzer);
    Path indexPath = Paths.get("indexdir");
    Directory directory;
    try {
        directory = FSDirectory.open(indexPath);
        IndexWriter indexWriter = new IndexWriter(directory, icw);
        indexWriter.deleteDocuments(new Term(field, key));
        indexWriter.commit();
        indexWriter.close();
        System.out.println("删除完成!");
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

除此之外IndexWriter还提供了以下方法：

• DeleteDocuments(Query query):根据Query条件来删除单个或多个Document
• DeleteDocuments(Query[] queries):根据Query条件来删除单个或多个Document
• DeleteDocuments(Term term):根据Term来删除单个或多个Document
• DeleteDocuments(Term[] terms):根据Term来删除单个或多个Document
• DeleteAll():删除所有的Document

更新Lucene索引

使用IndexWriter进行Document删除操作时，文档并不会立即被删除，而是把这个删除动作缓存起来，当IndexWriter.Commit()或IndexWriter.Close()时，删除操作才会被真正执行。
索引更新操作实质上是先删除索引，再重新建立新的文档，示例代码如下：

import java.nio.file.Path;
import java.nio.file.Paths;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
mport org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import tup.lucene.ik.IKAnalyzer6x;
public class UpdateIndex {
public static void main(String[] args) {
    Analyzer analyzer = new IKAnalyzer6x();
    IndexWriterConfig icw = new IndexWriterConfig(analyzer);
    Path indexPath = Paths.get("indexdir");
    Directory directory;
    try {
        directory = FSDirectory.open(indexPath);
        IndexWriter indexWriter = new IndexWriter(directory, icw);
        Document doc = new Document();
        doc.add(new TextField("id","2", Store.YES));
        doc.add(new TextField("title", " 北京大学开学迎来4380名新生",    
             Store.YES));
        doc.add(new TextField("content", " 昨天，北京大学迎来4380名来自全  
     国各地及数十个国家的本科新生。其中，农村学生共700余名，为近年最 
     多...", Store.YES));
        indexWriter.updateDocument(new Term("title", "北大"), doc);
        indexWriter.commit();
        indexWriter.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
}

上面的代码中我们新建了一个IndexWriter对象和Document对象，通过updateDocument()方法完成更新操作。Term对象用于定位文档，查找title中含有“北大”的文档，然后用新的文档替换原文档，这样就完成了索引的更新操作。