lucene学习之针对多索引的搜索

在实际应用中，很多应用程序保持多个分离的Lucene索引，但有需要在搜索过程中能够将结果合并输出，比如新闻网站每天都会建立不同索引，但是搜索一个月的新闻时就需要合并输出结果。这时可以使用如下方式：

mreader = new MultiReader(readera,readern);
        searcher = new IndexSearcher(mreader);//4.0以后的MultiSearcher替换成这样

可以看到我们需要使用MultiReader这个类，将读不同索引的reader封装在一块。
下面是实现代码

import java.io.IOException;

import junit.framework.TestCase;

import org.apache.lucene.analysis.*;
import org.apache.lucene.analysis.core.*;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.StringField;
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.MultiReader;
import org.apache.lucene.search.*;
import org.apache.lucene.store.*;


public class MultiSearcherTest extends TestCase{
    private static IndexSearcher searcher;
    static IndexReader readera;
    static IndexReader readern;
    static MultiReader mreader;

    public static void testMulti() throws IOException{
        String[] animals = {
                "aardvark","beaver","coati","dog",
                "elephant","frog","gila monster",
                "horse","iguana","javelina","kangroo",
                "lemur","moose","rematode","orca",
                "python","quoka","rat","scorpion",
                "tarantula","uromastyx","vicuna",
                "walrus","xiphias","yak","zebra"
        };
        Analyzer analyzer = new WhitespaceAnalyzer();
        Directory aTOmDirectory = new RAMDirectory();//建立两个目录
        Directory nTOzDirectory = new RAMDirectory();
        IndexWriterConfig configa = new IndexWriterConfig(analyzer);
        IndexWriterConfig confign = new IndexWriterConfig(analyzer);
        IndexWriter aTOmWriter = new IndexWriter(aTOmDirectory,configa);
        IndexWriter nTOzWriter = new IndexWriter(nTOzDirectory,confign);

        for(int i = animals.length - 1;i >= 0;i--){
            Document doc = new Document();
            String animal  = animals[i];
            doc.add(new StringField("animal",animal,Field.Store.YES));
            if(animal.charAt(0) < 'n'){
                aTOmWriter.addDocument(doc);
            }else{ 
                nTOzWriter.addDocument(doc);
            }
        }


        readera = DirectoryReader.open(aTOmWriter,true);
        readern = DirectoryReader.open(nTOzWriter,true);
        aTOmWriter.close();
        nTOzWriter.close();
        mreader = new MultiReader(readera,readern);
        searcher = new IndexSearcher(mreader);//4.0以后的MultiSearcher替换成这样
        TermRangeQuery query = TermRangeQuery.newStringRange("animal","h","t",true,true);
        TopDocs hits = searcher.search(query, 10);
        System.out.println("一共搜索到结果："+hits.totalHits+"条");
        for(ScoreDoc s:hits.scoreDocs){
            Document doc = searcher.doc(s.doc);//通过序号得到文件
            System.out.println("序号为"+s.doc+"   "+"animal:"+doc.get("animal"));
        }
        assertEquals("tarantula not included",12,hits.totalHits);
    }

    public static void main(String args[]) throws IOException{
        testMulti();
    }
}

TermRangeQuery类查询包含从h到t开头的动物名称，匹配的文档来自于两个不同的索引。结果如下：

当然上面程序是一个searcher单线程操作，也可以使用多线程的办法，lucene5中提供了ParalleLeafReader类。