Lucene4.10使用教程(十一)：Lucene的近实时搜索_综合

近实时搜索(Near real time search)表示当索引数据发生变化时，Lucene能及时把这种变化反映到客户进行查询的结果中。

实现原理：
只有Index Writer上的commit操作才会导致ram directory上的数据完全同步到文件。Index Writer提供了实时获得reader的API，这个调用将导致flush操作，生成新的segment，但不会commit（fsync），从而减少了IO。新的segment被加入到新生成的

reader里。从返回的reader里，可以看到更新。所以，只要每次新的搜索都从IndexWriter获得一个新的reader，就可以搜索到最新的内容。这一操作的开销仅仅是flush，相对commit来说，开销很小。

Lucene的index组织方式为一个index目录下的多个segment。新的doc会加入新的segment里，这些新的小segment每隔一段时间就合并起来。因为合并，总的segment数

量保持的较小，总体search速度仍然很快。为了防止读写冲突，lucene只创建新的segment，并在任何active的reader不在使用后删除掉老的segment。

flush是把数据写入到操作系统的缓冲区，只要缓冲区不满，就不会有硬盘操作，相对轻量级操作。

commit是把所有内存缓冲区的数据写入到硬盘，是完全的硬盘操作，重量级操作。

package com.johnny.lucene05.lucene_plugin.nrt;

import java.io.File;
import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.IntField;
import org.apache.lucene.document.LongField;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TrackingIndexWriter;
import org.apache.lucene.search.ControlledRealTimeReopenThread;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.ReferenceManager;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.SearcherFactory;
import org.apache.lucene.search.SearcherManager;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;

/**
* NRT（near real time）近实时搜索测试
* @author Johnny
*
*/
public class NearRealTimeSearch {
   private static Version Lucene_Version = Version.LUCENE_4_10_2;
   private String[] ids = {"1","2","3","4","5","6"};
   private String[] emails = {"aa@itat.org","bb@itat.org","cc@cc.org","dd@sina.org","ee@zttc.edu","ff@itat.org"};
   private String[] contents = {
           "welcome to visited the space,I like book",
           "hello boy, I like pingpeng ball",
           "my name is cc I like game",
           "I like football",
           "I like football and I like basketball too",
           "I like movie and swim"
   };
   private Date[] dates = null;
   private int[] attachs = {2,3,1,4,5,5};
   private String[] names = {"zhangsan","lisi","john","jetty","mike","jake"};
   private Directory directory = null;
   IndexWriter writer = null;

   /**nrt init**/
   private TrackingIndexWriter trackingIndexWriter = null;
   private ReferenceManager<IndexSearcher> reMgr = null;//类似于Lucene3.x中的NrtManager
   private ControlledRealTimeReopenThread<IndexSearcher> crt = null;

   private void setDates() {
       SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
       try {
           dates = new Date[ids.length];
           dates[0] = sdf.parse("2010-02-19");
           dates[1] = sdf.parse("2012-01-11");
           dates[2] = sdf.parse("2011-09-19");
           dates[3] = sdf.parse("2010-12-22");
           dates[4] = sdf.parse("2012-01-01");
           dates[5] = sdf.parse("2011-05-19");
       } catch (ParseException e) {
           e.printStackTrace();
       }
   }
   //数据初始化
   public NearRealTimeSearch(){
       setDates();

       try{
           directory = FSDirectory.open(new File("/Users/ChinaMWorld/Desktop/index/"));
           writer = new IndexWriter(directory, new IndexWriterConfig(Lucene_Version, new StandardAnalyzer()));

           trackingIndexWriter = new TrackingIndexWriter(writer);
           reMgr = new SearcherManager(writer, true, new SearcherFactory());
           /**在0.025s~5.0s之间重启一次线程，这个是时间的最佳实践**/
           crt = new ControlledRealTimeReopenThread<>(trackingIndexWriter, reMgr, 5.0,0.025);
           crt.setDaemon(true);//设置为后台服务
           crt.setName("Index update to disk");//线程名称
           crt.start();//线程启动

       }catch(Exception e){
           e.printStackTrace();
       }

   }
   /**
   * 定期提交内存中得索引到硬盘上，防止丢失
   */
   public void commit(){
       try {
           writer.commit();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }

   /**建立索引
   * 要实现search nrt,需要使用TrackIndexWriter保存document，同时Writer也不需要关闭。
   *
   * **/
   public void index(boolean isNew) {
       if(isNew){
           try {
               Document doc = null;
               for(int i=0;i<ids.length;i++) {
                   doc = new Document();
                   doc.add(new StringField("id",ids[i],Store.YES));
                   doc.add(new StringField("email", emails[i],Store.YES));
                   doc.add(new TextField("content", contents[i], Store.NO));
                   doc.add(new StringField("name",names[i], Store.YES));
                   //存储数字
                   doc.add(new IntField("attach",attachs[i], Store.YES));
                   //存储日期
                   doc.add(new LongField("date", dates[i].getTime(), Store.YES));
                   //使用trackingIndexWriter创建document
                   trackingIndexWriter.addDocument(doc);
               }
           } catch (IOException e) {
               e.printStackTrace();
           } finally{
               commit();//首次创建，提交索引,只有提交后，才会在索引片段中也将信息改变
           }
       }
   }


   /***查询**/
   public void query() {
       IndexSearcher is = getSearcher();

       try {
           //通过reader可以有效的获取到文档的数量
           System.out.println("numDocs:"+is.getIndexReader().numDocs());
           System.out.println("maxDocs:"+is.getIndexReader().maxDoc());
           System.out.println("deleteDocs:"+is.getIndexReader().numDeletedDocs());
       } catch (Exception e) {
           e.printStackTrace();
       }finally{
           try {
               reMgr.release(is);
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   }
   /**删除
   * 使用trackIndexWriter进行数据删除，也不需要关闭Writer
   * **/
   public void delete(){
       try{
           trackingIndexWriter.deleteDocuments(new Term("id","2"));
       }catch(Exception e){
           e.printStackTrace();
       }
   }


   /**修改
   * 使用trackIndexWriter进行修改，不需要关闭writer
   * **/
   public void update(){
       try{
           Document doc = new Document();
           /*
           * Lucene并没有提供更新，这里的更新操作其实是如下两个操作的合集
           * 先删除之后再添加
           */
           doc.add(new StringField("id", "21", Store.YES));
           doc.add(new TextField("email", "aa.bb@s", Store.YES));
           doc.add(new TextField("content", "update content like", Store.NO));
           doc.add(new StringField("name", "jackson", Store.YES));
           trackingIndexWriter.updateDocument(new Term("id","1"), doc);
       }catch(Exception e){
           e.printStackTrace();
       }
   }
   /**使用单例获取IndexSearch **/
   public IndexSearcher getSearcher() {
       IndexSearcher is = null;
       try {
           if(is==null) {
               reMgr.maybeRefresh();//刷新reMgr,获取最新的IndexSearcher
               is = reMgr.acquire();

           }
       } catch (IOException e) {
           e.printStackTrace();
       }
       if(is == null){
           throw new RuntimeException("indexSearcher is null!!!!");
       }
       return is;

   }

   /** 查询
   *
   * 查询时search如果使用完成，需要将search释放会searchFactory中，使用reMgr。release(indexSearcher)进行释放
   * **/
   public void search(){
       IndexSearcher is = getSearcher();
       try {
           TermQuery query = new TermQuery(new Term("content","like"));
           TopDocs tds = is.search(query, 10);
           for(ScoreDoc sd:tds.scoreDocs){
               Document doc = is.doc(sd.doc);
               System.out.println(doc.get("id")+"---->"+
                       doc.get("name")+"["+doc.get("email")+"]-->"+doc.get("id")+","+
                       doc.get("attach")+","+doc.get("date")+"," +doc.getValues("email")[0]);
           }
       } catch (IOException e) {
           e.printStackTrace();
       } finally{
           try {
               reMgr.release(is);
           } catch (IOException e) {
               e.printStackTrace();
           }
       }

   }
   /**
   * 关闭初始化线程的处理
   */
   public void close(){
       //stop the re-open thread
       crt.interrupt();
       crt.close();
       //close the indexWriter,commit 所有有过修改的内容
       try {
           writer.commit();
           writer.close();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }
}

测试方法：

package com.johnny.lucene05.lucene_plugin.nrt;

import org.junit.Before;
import org.junit.Test;

public class NearRealTimeSearchTest {
   private static NearRealTimeSearch ns =null;
   @Before
   public void init(){
       ns = new NearRealTimeSearch();
   }
   @Test
   public void testIndex(){
       ns.index(true);
   }

   @Test
   public void testSearch(){
       ns.query();
       for(int i=0;i<10;i++){
           ns.search();
           System.out.println(i+"--------------------");
           ns.delete();
           if(i==3){
               ns.update();
               ns.query();
           }
           try {
               Thread.sleep(5000);
           } catch (InterruptedException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
           }
       }
       ns.commit();
       ns.query();
   }
   @Test
   public void close(){
       ns.close();
   }
   @Test
   public void testQuery(){
       ns.query();
   }
}