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一步一步跟我学习lucene(18)---lucene索引时join和查询时join使用示例

时间:2015-06-04 07:31:12      阅读:163      评论:0      收藏:0      [点我收藏+]

标签:lucene   join查询   一步一步跟我学lucene   

了解sql的朋友都知道,我们在查询的时候可以采用join查询,即对有一定关联关系的对象进行联合查询来对多维的数据进行整理。这个联合查询的方式挺方便的,跟我们现实生活中的托人找关系类似,我们想要完成一件事,先找自己的熟人,然后通过熟人在一次找到其他,最终通过这种手段找到想要联系到的人。有点类似于”世间万物皆有联系“的感觉。

lucene的join包提供了索引时join和查询时join的功能;

Index-time join

大意是索引时join提供了查询时join的支持,且IndexWriter.addDocuments()方法调用时被join的documents以单个document块存储索引。索引时join对普通文本内容(如xml文档或数据库表)是方便可用的。特别是对类似于数据库的那种多表关联的情况,我们需要对提供关联关系的列提供join支持;

在索引时join的时候,索引中的documents被分割成parent documents(每个索引块的最后一个document)和child documents (除了parent documents外的所有documents).  由于lucene并不记录doc块的信息,我们需要提供一个Filter来标示parent documents。

在搜索结果的时候,我们利用ToParentBlockJoinQuery来从child query到parent document space来remap/join对应的结果。

如果我们只关注匹配查询条件的parent documents,我们可以用任意的collector来采集匹配到的parent documents;如果我们还想采集匹配parent document查询条件的child documents,我们就需要利用ToParentBlockJoinCollector来进行查询;一旦查询完成,我们可以利用ToParentBlockJoinCollector.getTopGroups()来获取匹配条件的TopGroups.

Query-time joins

查询时join是基于索引词,其实现有两步:

  • 第一步先从匹配fromQuery的fromField中采集所有的数据;
  • 从第一步得到的数据中筛选出所有符合条件的documents

查询时join接收一下输入参数:

  • fromField:fromField的名称,即要join的documents中的字段;
  • formQuery: 用户的查询条件
  • multipleValuesPerDocument: fromField在document是否是多个值
  • scoreMode:定义other join side中score是如何被使用的。如果不关注scoring,我们只需要设置成ScoreMode.None,此种方式会忽略评分因此会更高效和节约内存;
  • toField:toField的名称,即要join的toField的在对应的document中的字段

通常查询时join的实现类似于如下:

   String fromField = "from"; // Name of the from field
   boolean multipleValuesPerDocument = false; // Set only yo true in the case when your fromField has multiple values per document in your index
   String toField = "to"; // Name of the to field
   ScoreMode scoreMode = ScoreMode.Max // Defines how the scores are translated into the other side of the join.
   Query fromQuery = new TermQuery(new Term("content", searchTerm)); // Query executed to collect from values to join to the to values
 
   Query joinQuery = JoinUtil.createJoinQuery(fromField, multipleValuesPerDocument, toField, fromQuery, fromSearcher, scoreMode);
   TopDocs topDocs = toSearcher.search(joinQuery, 10); // Note: toSearcher can be the same as the fromSearcher
   // Render topDocs...

查询示例

这里我们模拟6组数据,示例代码如下

package com.lucene.index.test;

import static org.junit.Assert.assertEquals;

import java.nio.file.Paths;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.SortedDocValuesField;
import org.apache.lucene.document.TextField;
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.IndexWriterConfig.OpenMode;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.search.join.JoinUtil;
import org.apache.lucene.search.join.ScoreMode;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.BytesRef;
import org.junit.Test;

public class TestJoin {
	@Test
	public void testSimple() throws Exception {
	    final String idField = "id";
	    final String toField = "productId";

	    Directory dir = FSDirectory.open(Paths.get("index"));
	    Analyzer analyzer = new StandardAnalyzer();
	    IndexWriterConfig config = new IndexWriterConfig(analyzer);
	    config.setOpenMode(OpenMode.CREATE);
	    IndexWriter w = new IndexWriter(dir, config);

	    // 0
	    Document doc = new Document();
	    doc.add(new TextField("description", "random text", Field.Store.YES));
	    doc.add(new TextField("name", "name1", Field.Store.YES));
	    doc.add(new TextField(idField, "1", Field.Store.YES));
	    doc.add(new SortedDocValuesField(idField, new BytesRef("1")));
	    
	    w.addDocument(doc);

	    // 1
	    Document doc1 = new Document();
	    doc1.add(new TextField("price", "10.0", Field.Store.YES));
	    doc1.add(new TextField(idField, "2", Field.Store.YES));
	    doc1.add(new SortedDocValuesField(idField, new BytesRef("2")));
	    doc1.add(new TextField(toField, "1", Field.Store.YES));
	    doc1.add(new SortedDocValuesField(toField, new BytesRef("1")));
	    
	    w.addDocument(doc1);

	    // 2
	    Document doc2 = new Document();
	    doc2.add(new TextField("price", "20.0", Field.Store.YES));
	    doc2.add(new TextField(idField, "3", Field.Store.YES));
	    doc2.add(new SortedDocValuesField(idField, new BytesRef("3")));
	    doc2.add(new TextField(toField, "1", Field.Store.YES));
	    doc2.add(new SortedDocValuesField(toField, new BytesRef("1")));
	    
	    w.addDocument(doc2);

	    // 3
	    Document doc3 = new Document();
	    doc3.add(new TextField("description", "more random text", Field.Store.YES));
	    doc3.add(new TextField("name", "name2", Field.Store.YES));
	    doc3.add(new TextField(idField, "4", Field.Store.YES));
	    doc3.add(new SortedDocValuesField(idField, new BytesRef("4")));
	    
	    w.addDocument(doc3);
	    

	    // 4
	    Document doc4 = new Document();
	    doc4.add(new TextField("price", "10.0", Field.Store.YES));
	    doc4.add(new TextField(idField, "5", Field.Store.YES));
	    doc4.add(new SortedDocValuesField(idField, new BytesRef("5")));
	    doc4.add(new TextField(toField, "4", Field.Store.YES));
	    doc4.add(new SortedDocValuesField(toField, new BytesRef("4")));
	    w.addDocument(doc4);

	    // 5
	    Document doc5 = new Document();
	    doc5.add(new TextField("price", "20.0", Field.Store.YES));
	    doc5.add(new TextField(idField, "6", Field.Store.YES));
	    doc5.add(new SortedDocValuesField(idField, new BytesRef("6")));
	    doc5.add(new TextField(toField, "4", Field.Store.YES));
	    doc5.add(new SortedDocValuesField(toField, new BytesRef("4")));
	    w.addDocument(doc5);
	    
	    //6
	    Document doc6 = new Document();
	    doc6.add(new TextField(toField, "4", Field.Store.YES));
	    doc6.add(new SortedDocValuesField(toField, new BytesRef("4")));
	    w.addDocument(doc6);
	    w.commit();
	    w.close();
	    IndexReader reader = DirectoryReader.open(dir);
	    IndexSearcher indexSearcher = new IndexSearcher(reader);
	    

	    // Search for product
	    Query joinQuery = JoinUtil.createJoinQuery(idField, false, toField, new TermQuery(new Term("name", "name2")), indexSearcher, ScoreMode.None);
	    System.out.println(joinQuery);
	    TopDocs result = indexSearcher.search(joinQuery, 10);
	    System.out.println("查询到的匹配数据:"+result.totalHits);
	    

	    joinQuery = JoinUtil.createJoinQuery(idField, false, toField, new TermQuery(new Term("name", "name1")), indexSearcher, ScoreMode.None);
	    result = indexSearcher.search(joinQuery, 10);
	    System.out.println("查询到的匹配数据:"+result.totalHits);
	    // Search for offer
	    joinQuery = JoinUtil.createJoinQuery(toField, false, idField, new TermQuery(new Term("id", "5")), indexSearcher, ScoreMode.None);
	    result = indexSearcher.search(joinQuery, 10);
	    System.out.println("查询到的匹配数据:"+result.totalHits);

	    indexSearcher.getIndexReader().close();
	    dir.close();
	  }

}

程序的运行结果如下:

查询到的匹配数据:3
查询到的匹配数据:2
查询到的匹配数据:1

以第一个查询为例:

我们在查询的时候先根据name=name2这个查询条件找到记录为doc3的document,由于查询的是toField匹配的,我们在根据doc3找到其toField的值为4,然后查询条件变为productId:4,找出除本条记录外的其他数据,结果正好为3,符合条件。

一步一步跟我学习lucene是对近期做lucene索引的总结,大家有问题的话联系本人的Q-Q:  891922381,同时本人新建Q-Q群:106570134(lucene,solr,netty,hadoop),如蒙加入,不胜感激,大家共同探讨,本人争取每日一博,希望大家持续关注,会带给大家惊喜的




一步一步跟我学习lucene(18)---lucene索引时join和查询时join使用示例

标签:lucene   join查询   一步一步跟我学lucene   

原文地址:http://blog.csdn.net/wuyinggui10000/article/details/46336417

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