一步一步跟我学习lucene（7）---lucene搜索之IndexSearcher构建过程

IndexSearcher

搜索引擎的构建分为索引内容和查询索引两个大方面，这里要介绍的是lucene索引查询器即IndexSearcher的构建过程；

首先了解下IndexSearcher：

• IndexSearcher提供了对单个IndexReader的查询实现；
• 我们对索引的查询，可以通过调用search(Query,n)或者search(Query,Filter,n)方法；
• 在索引内容变动不大的情况下，我们可以对索引的搜索采用单个IndexSearcher共享的方式来提升性能；
• 如果索引有变动，我们就需要使用DirectoryReader.openIfChanged(DirectoryReader)来获取新的reader，然后创建新的IndexSearcher对象；
• 为了使查询延迟率低，我们最好使用近实时搜索的方法（此时我们的DirectoryReader的构建就要采用DirectoryReader.open(IndexWriter, boolean)）

• IndexSearcher实例是完全线程安全的,这意味着多个线程可以并发调用任何方法。如果需要外部同步,无需添加IndexSearcher的同步；

IndexSearcher的创建过程

• 根据索引文件路径创建FSDirectory的实例，返回的FSDirectory实例跟系统或运行环境有关，对于Linux, MacOSX, Solaris, and Windows 64-bit JREs返回的是一个MMapDirectory实例，对于其他非windows JREs环境返回的是NIOFSDirectory，而对于其他Windows的JRE环境返回的是SimpleFSDirectory，其执行效率依次降低
• 接着DirectoryReader根据获取到的FSDirectory实例读取索引文件并得到DirectoryReader对象；DirectoryReader的open方法返回实例的原理：读取索引目录中的Segments文件内容，倒序遍历SegmentInfos并填充到SegmentReader（IndexReader的一种实现）数组，并构建StandardDirectoryReader的实例
• 有了IndexReader，IndexSearcher对象实例化就手到拈来了，new IndexSearcher(DirectoryReader)就可以得到其实例；如果我们想提高IndexSearcher的执行效率可以new IndexSearcher(DirecotoryReader,ExcuterService)来创建IndexSearcher对象，这样做的好处为对每块segment采用了分工查询，但是要注意IndexSearcher并不维护ExcuterService的生命周期，我们还需要自行调用ExcuterService的close/awaitTermination

相关实践

以下是根据IndexSearcher相关的构建过程及其特性编写的一个搜索的工具类

package com.lucene.search;

import java.io.File;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.concurrent.ExecutorService;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.MultiReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.BooleanClause.Occur;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.NumericRangeQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.SortField.Type;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.search.TopFieldCollector;
import org.apache.lucene.store.FSDirectory;

import com.lucene.index.IndexUtil;

public class SearchUtil {
	public static final Analyzer analyzer = new StandardAnalyzer();
	/**获取IndexSearcher对象（适合单索引目录查询使用）
	 * @param indexPath 索引目录
	 * @return
	 * @throws IOException
	 * @throws InterruptedException 
	 */
	public static IndexSearcher getIndexSearcher(String indexPath,ExecutorService service,boolean realtime) throws IOException, InterruptedException{
		DirectoryReader reader = DirectoryReader.open(IndexUtil.getIndexWriter(indexPath, true), realtime);
		IndexSearcher searcher = new IndexSearcher(reader,service);
		if(service != null){
			service.shutdown();
		}
		return searcher;
	}
	
	/**多目录多线程查询
	 * @param parentPath 父级索引目录
	 * @param service 多线程查询
	 * @return
	 * @throws IOException
	 * @throws InterruptedException 
	 */
	public static IndexSearcher getMultiSearcher(String parentPath,ExecutorService service,boolean realtime) throws IOException, InterruptedException{
		MultiReader multiReader;
		File file = new File(parentPath);
		File[] files = file.listFiles();
		IndexReader[] readers = new IndexReader[files.length];
		if(!realtime){
			for (int i = 0 ; i < files.length ; i ++) {
				readers[i] = DirectoryReader.open(FSDirectory.open(Paths.get(files[i].getPath(), new String[0])));
			}
		}else{
			for (int i = 0 ; i < files.length ; i ++) {
				readers[i] = DirectoryReader.open(IndexUtil.getIndexWriter(files[i].getPath(), true), true);
			}
		}
	
		multiReader = new MultiReader(readers);
		IndexSearcher searcher = new IndexSearcher(multiReader,service);
		if(service != null){
			service.shutdown();
		}
		return searcher;
	}
	
	/**从指定配置项中查询
	 * @return
	 * @param analyzer 分词器
	 * @param field 字段
	 * @param fieldType	字段类型
	 * @param queryStr 查询条件
	 * @param range 是否区间查询
	 * @return
	 */
	public static Query getQuery(String field,String fieldType,String queryStr,boolean range){
		Query q = null;
		if(queryStr != null && !"".equals(queryStr)){
			if(range){
				String[] strs = queryStr.split("\\|");
				if("int".equals(fieldType)){
					int min = new Integer(strs[0]);
					int max = new Integer(strs[1]);
					q = NumericRangeQuery.newIntRange(field, min, max, true, true);
				}else if("double".equals(fieldType)){
					Double min = new Double(strs[0]);
					Double max = new Double(strs[1]);
					q = NumericRangeQuery.newDoubleRange(field, min, max, true, true);
				}else if("float".equals(fieldType)){
					Float min = new Float(strs[0]);
					Float max = new Float(strs[1]);
					q = NumericRangeQuery.newFloatRange(field, min, max, true, true);
				}else if("long".equals(fieldType)){
					Long min = new Long(strs[0]);
					Long max = new Long(strs[1]);
					q = NumericRangeQuery.newLongRange(field, min, max, true, true);
				}
			}else{
				if("int".equals(fieldType)){
					q = NumericRangeQuery.newIntRange(field, new Integer(queryStr), new Integer(queryStr), true, true);
				}else if("double".equals(fieldType)){
					q = NumericRangeQuery.newDoubleRange(field, new Double(queryStr), new Double(queryStr), true, true);
				}else if("float".equals(fieldType)){
					q = NumericRangeQuery.newFloatRange(field, new Float(queryStr), new Float(queryStr), true, true);
				}else{
					Term term = new Term(field, queryStr);
					q = new TermQuery(term);
				}
			}
		}else{
			q= new MatchAllDocsQuery();
		}
		
		System.out.println(q);
		return q;
	}
	/**多条件查询类似于sql in
	 * @param querys
	 * @return
	 */
	public static Query getMultiQueryLikeSqlIn(Query ... querys){
		BooleanQuery query = new BooleanQuery();
		for (Query subQuery : querys) {
			query.add(subQuery,Occur.SHOULD);
		}
		return query;
	}
	
	/**多条件查询类似于sql and
	 * @param querys
	 * @return
	 */
	public static Query getMultiQueryLikeSqlAnd(Query ... querys){
		BooleanQuery query = new BooleanQuery();
		for (Query subQuery : querys) {
			query.add(subQuery,Occur.MUST);
		}
		return query;
	}
	/**对多个条件进行排序构建排序条件
	 * @param fields
	 * @param type
	 * @param reverses
	 * @return
	 */
	public static Sort getSortInfo(String[] fields,Type[] types,boolean[] reverses){
		SortField[] sortFields = null;
		int fieldLength = fields.length;
		int typeLength = types.length;
		int reverLength = reverses.length;
		if(!(fieldLength == typeLength) || !(fieldLength == reverLength)){
			return null;
		}else{
			sortFields = new SortField[fields.length];
			for (int i = 0; i < fields.length; i++) {
				sortFields[i] = new SortField(fields[i], types[i], reverses[i]);
			}
		}
		return new Sort(sortFields);
	}
	/**根据查询器、查询条件、每页数、排序条件进行查询
	 * @param query 查询条件
	 * @param first 起始值
	 * @param max 最大值
	 * @param sort 排序条件
	 * @return
	 */
	public static TopDocs getScoreDocsByPerPageAndSortField(IndexSearcher searcher,Query query, int first,int max, Sort sort){
		try {
			if(query == null){
				System.out.println(" Query is null return null ");
				return null;
			}
			TopFieldCollector collector = null;
			if(sort != null){
				collector = TopFieldCollector.create(sort, first+max, false, false, false);
			}else{
				sort = new Sort(new SortField[]{new SortField("modified", SortField.Type.LONG)});
				collector = TopFieldCollector.create(sort, first+max, false, false, false);
			}
			searcher.search(query, collector);
			return collector.topDocs(first, max);
		} catch (IOException e) {
			// TODO Auto-generated catch block
		}
		return null;
	}
	
	/**获取上次索引的id,增量更新使用
	 * @return
	 */
	public static Integer getLastIndexBeanID(IndexReader multiReader){
		Query query = new MatchAllDocsQuery();
		IndexSearcher searcher = null;
		searcher = new IndexSearcher(multiReader);
		SortField sortField = new SortField("id", SortField.Type.INT,true);
		Sort sort = new Sort(new SortField[]{sortField});
		TopDocs docs = getScoreDocsByPerPageAndSortField(searcher,query, 0, 1, sort);
		ScoreDoc[] scoreDocs = docs.scoreDocs;
		int total = scoreDocs.length;
		if(total > 0){
			ScoreDoc scoreDoc = scoreDocs[0];
			Document doc = null;
			try {
				doc = searcher.doc(scoreDoc.doc);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			return new Integer(doc.get("id"));
		}
		return 0;
	}
}

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