lucene-分页查询

程序员文章站 2022-07-09 09:52:56

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两种方式
分页查询是很常见的需求，比如要查询第10页，每页10条数据。
Lucene 分页通常来讲有两种方式：
第一种是把100条数据查出来，然后取最后10条。优点是快，缺点是对内存消耗大。
第二种是把第90条查询出来，然后基于这一条，通过searchAfter方法查询10条数据。优点是内存消耗小，缺点是比第一种更慢

第一种

	private static ScoreDoc[] pageSearch1(Query query, IndexSearcher searcher, int pageNow, int pageSize)
			throws IOException {
		TopDocs topDocs = searcher.search(query, pageNow*pageSize);
		 System.out.println("查询到的总条数\t"+topDocs.totalHits);
		 ScoreDoc [] alllScores = topDocs.scoreDocs;
		 List<ScoreDoc> hitScores = new ArrayList<>();
		
		 
		 int start = (pageNow -1)*pageSize ;
		 int end = pageSize*pageNow;
		 for(int i=start;i<end;i++)
			 hitScores.add(alllScores[i]);
		
		
		 ScoreDoc[] hits = hitScores.toArray(new ScoreDoc[]{});
		return hits;
	}

一共查出 pageNow*pageSize条，然后取最后pageSize条

public class TestLucene {
 
    public static void main(String[] args) throws Exception {
        // 1. 准备中文分词器
        IKAnalyzer analyzer = new IKAnalyzer();
        // 2. 索引
        Directory index = createIndex(analyzer);
 
        // 3. 查询器
         
            String keyword = "手机";
            System.out.println("当前关键字是："+keyword);
            Query query = new QueryParser( "name", analyzer).parse(keyword);
 
            // 4. 搜索
            IndexReader reader = DirectoryReader.open(index);
            IndexSearcher searcher=new IndexSearcher(reader);
            int pageNow = 1;
            int pageSize = 10;
             
            ScoreDoc[] hits = pageSearch1(query, searcher, pageNow, pageSize);
             
            // 5. 显示查询结果
            showSearchResults(searcher, hits,query,analyzer);
            // 6. 关闭查询
            reader.close();
         
    }
 
    private static ScoreDoc[] pageSearch1(Query query, IndexSearcher searcher, int pageNow, int pageSize)
            throws IOException {
        TopDocs topDocs = searcher.search(query, pageNow*pageSize);
         System.out.println("查询到的总条数\t"+topDocs.totalHits);
         ScoreDoc [] alllScores = topDocs.scoreDocs;
 
         List<ScoreDoc> hitScores = new ArrayList<>();
         
         int start = (pageNow -1)*pageSize ;
         int end = pageSize*pageNow;
         for(int i=start;i<end;i++)
             hitScores.add(alllScores[i]);
         
         ScoreDoc[] hits = hitScores.toArray(new ScoreDoc[]{});
        return hits;
    }
     
    private static void showSearchResults(IndexSearcher searcher, ScoreDoc[] hits, Query query, IKAnalyzer analyzer) throws Exception {
        System.out.println("找到 " + hits.length + " 个命中.");
 
        SimpleHTMLFormatter simpleHTMLFormatter = new SimpleHTMLFormatter("<span style='color:red'>", "</span>");
        Highlighter highlighter = new Highlighter(simpleHTMLFormatter, new QueryScorer(query));
 
        System.out.println("找到 " + hits.length + " 个命中.");
        System.out.println("序号\t匹配度得分\t结果");
        for (int i = 0; i < hits.length; ++i) {
            ScoreDoc scoreDoc= hits[i];
            int docId = scoreDoc.doc;
            Document d = searcher.doc(docId);
            List<IndexableField> fields= d.getFields();
            System.out.print((i + 1) );
            System.out.print("\t" + scoreDoc.score);
            for (IndexableField f : fields) {
 
                if("name".equals(f.name())){
                    TokenStream tokenStream = analyzer.tokenStream(f.name(), new StringReader(d.get(f.name())));
                    String fieldContent = highlighter.getBestFragment(tokenStream, d.get(f.name()));
                    System.out.print("\t"+fieldContent);
                }
                else{
                    System.out.print("\t"+d.get(f.name()));
                }
            }
            System.out.println("<br>");
        }
    }
 
    private static Directory createIndex(IKAnalyzer analyzer) throws IOException {
        Directory index = new RAMDirectory();
        IndexWriterConfig config = new IndexWriterConfig(analyzer);
        IndexWriter writer = new IndexWriter(index, config);
        String fileName = "140k_products.txt";
        List<Product> products = ProductUtil.file2list(fileName);
        int total = products.size();
        int count = 0;
        int per = 0;
        int oldPer =0;
        for (Product p : products) {
            addDoc(writer, p);
            count++;
            per = count*100/total;
            if(per!=oldPer){
                oldPer = per;
                System.out.printf("索引中，总共要添加 %d 条记录，当前添加进度是： %d%% %n",total,per);
            }
             
            if(per>10)
                break;
             
        }
        writer.close();
        return index;
    }
 
    private static void addDoc(IndexWriter w, Product p) throws IOException {
        Document doc = new Document();
        doc.add(new TextField("id", String.valueOf(p.getId()), Field.Store.YES));
        doc.add(new TextField("name", p.getName(), Field.Store.YES));
        doc.add(new TextField("category", p.getCategory(), Field.Store.YES));
        doc.add(new TextField("price", String.valueOf(p.getPrice()), Field.Store.YES));
        doc.add(new TextField("place", p.getPlace(), Field.Store.YES));
        doc.add(new TextField("code", p.getCode(), Field.Store.YES));
        w.addDocument(doc);
    }
}

第二种

private static ScoreDoc[] pageSearch2(Query query, IndexSearcher searcher, int pageNow, int pageSize)
			throws IOException {
        int start = (pageNow - 1) * pageSize;
        if(0==start){
        	TopDocs topDocs = searcher.search(query, pageNow*pageSize);
        	return topDocs.scoreDocs;
        }
        // 查询数据， 结束页面自前的数据都会查询到，但是只取本页的数据
        TopDocs topDocs = searcher.search(query, start);
        //获取到上一页最后一条
        
        ScoreDoc preScore= topDocs.scoreDocs[start-1];
        //查询最后一条后的数据的一页数据
        topDocs = searcher.searchAfter(preScore, query, pageSize);
        return topDocs.scoreDocs;
        
	}

首先是边界条件，如果是第一页，就直接查询了。
如果不是第一页，那么就取start-1那一条，然后再根据它通过searchAfter 来查询

public class TestLucene {
 
    public static void main(String[] args) throws Exception {
        // 1. 准备中文分词器
        IKAnalyzer analyzer = new IKAnalyzer();
        // 2. 索引
        Directory index = createIndex(analyzer);
 
        // 3. 查询器
         
            String keyword = "手机";
            System.out.println("当前关键字是："+keyword);
            Query query = new QueryParser( "name", analyzer).parse(keyword);
 
            // 4. 搜索
            IndexReader reader = DirectoryReader.open(index);
            IndexSearcher searcher=new IndexSearcher(reader);
            int pageNow = 1;
            int pageSize = 10;
             
            ScoreDoc[] hits = pageSearch2(query, searcher, pageNow, pageSize);
             
            // 5. 显示查询结果
            showSearchResults(searcher, hits,query,analyzer);
            // 6. 关闭查询
            reader.close();
         
    }
 
    private static ScoreDoc[] pageSearch1(Query query, IndexSearcher searcher, int pageNow, int pageSize)
            throws IOException {
        TopDocs topDocs = searcher.search(query, pageNow*pageSize);
         System.out.println("查询到的总条数\t"+topDocs.totalHits);
         ScoreDoc [] alllScores = topDocs.scoreDocs;
 
         List<ScoreDoc> hitScores = new ArrayList<>();
         
         int start = (pageNow -1)*pageSize ;
         int end = pageSize*pageNow;
         for(int i=start;i<end;i++)
             hitScores.add(alllScores[i]);
         
         ScoreDoc[] hits = hitScores.toArray(new ScoreDoc[]{});
        return hits;
    }
     
    private static ScoreDoc[] pageSearch2(Query query, IndexSearcher searcher, int pageNow, int pageSize)
            throws IOException {
         
        int start = (pageNow - 1) * pageSize;
        if(0==start){
            TopDocs topDocs = searcher.search(query, pageNow*pageSize);
            return topDocs.scoreDocs;
        }
        // 查询数据， 结束页面自前的数据都会查询到，但是只取本页的数据
        TopDocs topDocs = searcher.search(query, start);
        //获取到上一页最后一条
         
        ScoreDoc preScore= topDocs.scoreDocs[start-1];
 
        //查询最后一条后的数据的一页数据
        topDocs = searcher.searchAfter(preScore, query, pageSize);
        return topDocs.scoreDocs;
         
    }
 
    private static void showSearchResults(IndexSearcher searcher, ScoreDoc[] hits, Query query, IKAnalyzer analyzer) throws Exception {
        System.out.println("找到 " + hits.length + " 个命中.");
 
        SimpleHTMLFormatter simpleHTMLFormatter = new SimpleHTMLFormatter("<span style='color:red'>", "</span>");
        Highlighter highlighter = new Highlighter(simpleHTMLFormatter, new QueryScorer(query));
 
        System.out.println("找到 " + hits.length + " 个命中.");
        System.out.println("序号\t匹配度得分\t结果");
        for (int i = 0; i < hits.length; ++i) {
            ScoreDoc scoreDoc= hits[i];
            int docId = scoreDoc.doc;
            Document d = searcher.doc(docId);
            List<IndexableField> fields= d.getFields();
            System.out.print((i + 1) );
            System.out.print("\t" + scoreDoc.score);
            for (IndexableField f : fields) {
 
                if("name".equals(f.name())){
                    TokenStream tokenStream = analyzer.tokenStream(f.name(), new StringReader(d.get(f.name())));
                    String fieldContent = highlighter.getBestFragment(tokenStream, d.get(f.name()));
                    System.out.print("\t"+fieldContent);
                }
                else{
                    System.out.print("\t"+d.get(f.name()));
                }
            }
            System.out.println("<br>");
        }
    }
 
    private static Directory createIndex(IKAnalyzer analyzer) throws IOException {
        Directory index = new RAMDirectory();
        IndexWriterConfig config = new IndexWriterConfig(analyzer);
        IndexWriter writer = new IndexWriter(index, config);
        String fileName = "140k_products.txt";
        List<Product> products = ProductUtil.file2list(fileName);
        int total = products.size();
        int count = 0;
        int per = 0;
        int oldPer =0;
        for (Product p : products) {
            addDoc(writer, p);
            count++;
            per = count*100/total;
            if(per!=oldPer){
                oldPer = per;
                System.out.printf("索引中，总共要添加 %d 条记录，当前添加进度是： %d%% %n",total,per);
            }
             
            if(per>10)
                break;
             
        }
        writer.close();
        return index;
    }
 
    private static void addDoc(IndexWriter w, Product p) throws IOException {
        Document doc = new Document();
        doc.add(new TextField("id", String.valueOf(p.getId()), Field.Store.YES));
        doc.add(new TextField("name", p.getName(), Field.Store.YES));
        doc.add(new TextField("category", p.getCategory(), Field.Store.YES));
        doc.add(new TextField("price", String.valueOf(p.getPrice()), Field.Store.YES));
        doc.add(new TextField("place", p.getPlace(), Field.Store.YES));
        doc.add(new TextField("code", p.getCode(), Field.Store.YES));
        w.addDocument(doc);
    }
}

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