Lucene5学习之CustomScoreQuery

      虽然前面我们已经集中学习过Query,但CustomScoreQuery当初略过了，今天就来学学这个Query.从类名上看，顾名思义，就大不略的猜得到它的干嘛用的。它是用来进行干预查询权重的，从而影响最终评分的，即评分公式中的queryNorm部分。

      一个索引文档的评分高低意味着它的价值大小，有价值的索引文档会优先返回并靠前显示，而影响评分的因素有Term在document中的出现频率，以及term在每个document中的出现频率，Term的权重等等，但这些因素都是固定的，并不会因为随着时间的改变而有所变化。比如你希望越是新出版的书籍权重应该越高，即出版日期距离当前时间越近权重越大。再比如你想实现我关注的用户发表的文章优先靠前显示，非关注用户发表的文章靠后显示等等，而CustomScoreQuery提供了这样一个接口来实现类似上述场景中的需求。你要做的就是

继承RecencyBoostCustomScoreQuery提供自己的CustomScoreProvider实现并重写其customScore方法，编写自己的实现逻辑。

      下面是使用示例：

package com.yida.framework.lucene5.function;

import java.io.IOException;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.NumericDocValues;
import org.apache.lucene.index.SortedDocValues;
import org.apache.lucene.queries.CustomScoreProvider;

public class RecencyBoostCustomScoreProvider extends CustomScoreProvider {
	//权重倍数
	private double multiplier;
	// 从1970-01-01至今的总天数
	private int day;
	// 最大过期天数
	private int maxDaysAgo;
	// 日期域的名称
	private String dayField;
	// 域缓存值
	private NumericDocValues publishDay;
	
	private SortedDocValues titleValues;

	public RecencyBoostCustomScoreProvider(LeafReaderContext context,double multiplier,int day,int maxDaysAgo,String dayField) {
		super(context);
		this.multiplier = multiplier;
		this.day = day;
		this.maxDaysAgo = maxDaysAgo;
		this.dayField = dayField;
		try {
			publishDay = context.reader().getNumericDocValues(dayField);
			titleValues = context.reader().getSortedDocValues("title2");
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * subQueryScore:指的是普通Query查询的评分
	 * valSrcScore：指的是FunctionQuery查询的评分
	 */
	@Override
	public float customScore(int docId, float subQueryScore, float valSrcScore)
			throws IOException {
		String title = titleValues.get(docId).utf8ToString();
		int daysAgo = (int) (day - publishDay.get(docId));
		//System.out.println(title + ":" + daysAgo + ":" + maxDaysAgo);
		//如果在6年之内
		if (daysAgo < maxDaysAgo) {
			float boost = (float) (multiplier * (maxDaysAgo - daysAgo) / maxDaysAgo);
			return (float) (subQueryScore * (1.0 + boost));
		}
		return subQueryScore;
	}
}

    

package com.yida.framework.lucene5.function;

import java.io.IOException;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.queries.CustomScoreProvider;
import org.apache.lucene.queries.CustomScoreQuery;
import org.apache.lucene.search.Query;

public class RecencyBoostCustomScoreQuery extends CustomScoreQuery {
	// 倍数
	private double multiplier;
	// 从1970-01-01至今的总天数
	private int day;
	// 最大过期天数
	private int maxDaysAgo;
	// 日期域的名称
	private String dayField;
	public RecencyBoostCustomScoreQuery(Query subQuery,double multiplier,int day,int maxDaysAgo,String dayField) {
		super(subQuery);
		this.multiplier = multiplier;
		this.day = day;
		this.maxDaysAgo = maxDaysAgo;
		this.dayField = dayField;
	}

	@Override
	protected CustomScoreProvider getCustomScoreProvider(
			LeafReaderContext context) throws IOException {
		return new RecencyBoostCustomScoreProvider(context,multiplier,day,maxDaysAgo,dayField);
	}
}

    

package com.yida.framework.lucene5.function;

import java.io.IOException;
import java.nio.file.Paths;
import java.util.Date;

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.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;

import com.yida.framework.lucene5.util.Constans;
/**
 * CustomScoreQuery测试
 * @author Lanxiaowei
 *
 */
public class CustomScoreQueryTest {
	
	public static void main(String[] args) throws IOException, ParseException {
		String indexDir = "C:/lucenedir";
		Directory directory = FSDirectory.open(Paths.get(indexDir));
	    IndexReader reader = DirectoryReader.open(directory);
	    IndexSearcher searcher = new IndexSearcher(reader);
	    
	    int day = (int) (new Date().getTime() / Constans.PRE_DAY_MILLISECOND);
	    QueryParser parser = new QueryParser("contents",new StandardAnalyzer());
	    Query query = parser.parse("java in action");       
	    Query customScoreQuery = new RecencyBoostCustomScoreQuery(query,2.0,day, 6*365,"pubmonthAsDay");
	    Sort sort = new Sort(new SortField[] {SortField.FIELD_SCORE,
	        new SortField("title2", SortField.Type.STRING)});
	    TopDocs hits = searcher.search(customScoreQuery, null, Integer.MAX_VALUE, sort,true,false);

	    for (int i = 0; i < hits.scoreDocs.length; i++) {
	    	//两种方式取Document都行，其实searcher.doc内部本质还是调用reader.document
	      //Document doc = reader.document(hits.scoreDocs[i].doc);
	    	Document doc = searcher.doc(hits.scoreDocs[i].doc);
	      System.out.println((1+i) + ": " +
	                         doc.get("title") +
	                         ": pubmonth=" +
	                         doc.get("pubmonth") +
	                         " score=" + hits.scoreDocs[i].score);
	    }
	    reader.close();
	    directory.close();
	}
}

    

package com.yida.framework.lucene5.sort;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.file.Paths;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Properties;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.BinaryDocValuesField;
import org.apache.lucene.document.DateTools;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.IntField;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.document.SortedDocValuesField;
import org.apache.lucene.document.SortedNumericDocValuesField;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.IndexWriterConfig.OpenMode;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.BytesRef;
/**
 * 创建测试索引
 * @author Lanxiaowei
 *
 */
public class CreateTestIndex {
	public static void main(String[] args) throws IOException {
		String dataDir = "C:/data";
		String indexDir = "C:/lucenedir";

		Directory dir = FSDirectory.open(Paths.get(indexDir));
		Analyzer analyzer = new StandardAnalyzer();
		IndexWriterConfig indexWriterConfig = new IndexWriterConfig(analyzer);
		indexWriterConfig.setOpenMode(OpenMode.CREATE_OR_APPEND);
		IndexWriter writer = new IndexWriter(dir, indexWriterConfig);

		List<File> results = new ArrayList<File>();
		findFiles(results, new File(dataDir));
		System.out.println(results.size() + " books to index");

		for (File file : results) {
			Document doc = getDocument(dataDir, file);
			writer.addDocument(doc);
		}
		writer.close();
		dir.close();

	}

	/**
	 * 查找指定目录下的所有properties文件
	 * 
	 * @param result
	 * @param dir
	 */
	private static void findFiles(List<File> result, File dir) {
		for (File file : dir.listFiles()) {
			if (file.getName().endsWith(".properties")) {
				result.add(file);
			} else if (file.isDirectory()) {
				findFiles(result, file);
			}
		}
	}

	/**
	 * 读取properties文件生成Document
	 * 
	 * @param rootDir
	 * @param file
	 * @return
	 * @throws IOException
	 */
	public static Document getDocument(String rootDir, File file)
			throws IOException {
		Properties props = new Properties();
		props.load(new FileInputStream(file));

		Document doc = new Document();

		String category = file.getParent().substring(rootDir.length());
		category = category.replace(File.separatorChar, '/');

		String isbn = props.getProperty("isbn");
		String title = props.getProperty("title");
		String author = props.getProperty("author");
		String url = props.getProperty("url");
		String subject = props.getProperty("subject");

		String pubmonth = props.getProperty("pubmonth");

		System.out.println("title:" + title + "\n" + "author:" + author + "\n" + "subject:" + subject + "\n"
				+ "pubmonth:" + pubmonth + "\n" + "category:" + category + "\n---------");

		doc.add(new StringField("isbn", isbn, Field.Store.YES));
		doc.add(new StringField("category", category, Field.Store.YES));
		doc.add(new SortedDocValuesField("category", new BytesRef(category)));
		doc.add(new TextField("title", title, Field.Store.YES));
		doc.add(new Field("title2", title.toLowerCase(), Field.Store.YES,
				Field.Index.NOT_ANALYZED_NO_NORMS,
				Field.TermVector.WITH_POSITIONS_OFFSETS));
		//doc.add(new BinaryDocValuesField("title2", new BytesRef(title.getBytes())));
		
		doc.add(new SortedDocValuesField("title2", new BytesRef(title.getBytes())));
		String[] authors = author.split(",");
		for (String a : authors) {
			doc.add(new Field("author", a, Field.Store.YES,
					Field.Index.NOT_ANALYZED,
					Field.TermVector.WITH_POSITIONS_OFFSETS));
		}

		doc.add(new Field("url", url, Field.Store.YES,
				Field.Index.NOT_ANALYZED_NO_NORMS));
		doc.add(new Field("subject", subject, Field.Store.YES,
				Field.Index.ANALYZED, Field.TermVector.WITH_POSITIONS_OFFSETS));

		doc.add(new IntField("pubmonth", Integer.parseInt(pubmonth),
				Field.Store.YES));
		doc.add(new NumericDocValuesField("pubmonth", Integer.parseInt(pubmonth)));
		Date d = null;
		try {
			d = DateTools.stringToDate(pubmonth);
		} catch (ParseException pe) {
			throw new RuntimeException(pe);
		}
		int day = (int) (d.getTime() / (1000 * 3600 * 24));
		doc.add(new IntField("pubmonthAsDay",day, Field.Store.YES));
		doc.add(new NumericDocValuesField("pubmonthAsDay", day));
		for (String text : new String[] { title, subject, author, category }) {
			doc.add(new Field("contents", text, Field.Store.NO,
					Field.Index.ANALYZED,
					Field.TermVector.WITH_POSITIONS_OFFSETS));
		}
		return doc;
	}

}

    重点在创建索引域那里，由于我们需要在CustomScoreQuery里获取指定域的所有值，随后根据文档ID去获取特定域的值，这里Lucene使用了FieldCache即域缓存，如果不用域缓存，我们需要根据docId通过IndexReader对象去索引目录读取每个段文件从而获取某个域的值，一个文档意味着一次磁盘IO，如果你索引文档数据量大的话，那后果将会很严重，你懂的，为了减少磁盘IO次数，Lucene引入了域缓存概念，其实内部就是用一个Map<String,Object> 来存储的，map的key就是域的名称，看源码：

     IndexReader.getNumericDocValues

 @Override
  public final NumericDocValues getNumericDocValues(String field) throws IOException {
    ensureOpen();
    Map<String,Object> dvFields = docValuesLocal.get();

    Object previous = dvFields.get(field);
    if (previous != null && previous instanceof NumericDocValues) {
      return (NumericDocValues) previous;
    } else {
      FieldInfo fi = getDVField(field, DocValuesType.NUMERIC);
      if (fi == null) {
        return null;
      }
      NumericDocValues dv = getDocValuesReader().getNumeric(fi);
      dvFields.put(field, dv);
      return dv;
    }
  }

    还有一点需要注意的是域缓存只对DocValuesField有效，这也是为什么创建索引代码那里需要add SortedDocValuesField,因为我们还需要根据该域进行排序，所以使用了SortedDocValuesField，

字符串类型可以用BinaryDocValuesField,数字类型可以使用NumericDocValuesField.域缓存是Lucene内部的一个高级API，对于用户来说，它是透明的，你只需要知道，使用DocValuesField可以利用域缓存来提升查询性能，但缓存也意味着需要有更多的内存消耗，所以在使用之前请进行性能测试，至于到底使不使用域缓存根据测试结果做好权衡。当你需要在Query查询内部去获取每个索引的某个域的值的时候，你就应该考虑使用域缓存。对于给定的IndexReader和指定的域，在首次访问域缓存的时候，会加载所有索引的该域的values放入缓存中(其实就是内存)，是根据indexReader和域名两者联合起来确定唯一性，换句话说，你应该在多次查询中维持同一个IndexReader对象，因为每一个IndexReader都会有一套域缓存，如果你每次都new一个新的IndexReader,你会在内存中N个域缓存，这无疑是在内存中埋了N颗定时乍弹，而且这些你也无法利用域缓存。

    

       如果你还有什么问题请加我Ｑ-Q：7-3-6-0-3-1-3-0-5，

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