lucene学习之针对多索引的搜索

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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：
运行结果
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。

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