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lucene搜索之expressions表达式处理

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lucene（17）—lucene搜索之expressions表达式处理

有时候我们在做lucene的结果展示的时候可能需要对多个列的内容进行计算，根据多个field对应的值做数值方面的运算。

lucene自4.6版本起，提供了用于运算的expression模块；

expression分为两部分：

  • org.apache.lucene.expressions：提供了字段绑定和相关的表达式参数传递的功能；
  • org.apache.lucene.expressions.js:提供了表达式定义的功能。

Expression类使用示例

Expression是提供document的运算的支持类；

我们的运算表达式和其绑定内容通常类似于如下：

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// compile an expression:
Expression expr = JavascriptCompiler.compile("sqrt(_score) + ln(popularity)");
// SimpleBindings just maps variables to SortField instances
SimpleBindings bindings = new SimpleBindings();    
bindings.add(new SortField("_score", SortField.Type.SCORE));
bindings.add(new SortField("popularity", SortField.Type.INT));
// create a sort field and sort by it (reverse order)
Sort sort = new Sort(expr.getSortField(bindings, true));
Query query = new TermQuery(new Term("body", "contents"));
searcher.search(query, null, 10, sort);

如上所示，我们对document中的_score和popularity两个字段进行值的运算，这里是对_score开平方之后和popularity的对数运算求和，运算方式的定义在第一行；

下边有定义了SimpleBindings，binding主要是对运算的数据进行数据绑定；

最终的查询结果是根据以上的运算结果采取倒排序的方式表达式说明表达式的构造可以采用如下的几种来进行组合：

数值型的

  • 加减乘除取模（+-*/%）等运算符
  • 移位运算符：| & ^ ~ << >> >>>
  • 布尔运算符（包括三目运算符）： && || ! ?:
  • 比较运算符：< <= == >= >
  • 数学运算函数：abs ceil exp floor ln log10 logn max min sqrt pow
  • 三角运算函数：acosh acos asinh asin atanh atan atan2 cosh cos sinh sin tanh tan
  • haversin公式
  • min,max函数

代码示例：

我写了一个测试程序，模拟长方形的运算并排序；

面积倒序排序；当面积相同时，按宽度倒序，长度倒序；

周长倒序排序；周长相同时，按宽度倒序，长度倒序；

示例程序如下：

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package com.lucene.expression;
 
import java.io.IOException;
import java.nio.file.Paths;
import java.text.ParseException;
 
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.IntField;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.expressions.Expression;
import org.apache.lucene.expressions.SimpleBindings;
import org.apache.lucene.expressions.js.JavascriptCompiler;
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.search.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
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.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.junit.Test;
 
 
public class LuceneExpressionTest{
	@Test
	public void index(){
		try {
			Directory directory = FSDirectory.open(Paths.get("index"));
			Analyzer analyzer = new StandardAnalyzer();
			IndexWriterConfig config = new IndexWriterConfig(analyzer);
			config.setOpenMode(OpenMode.CREATE_OR_APPEND);
			IndexWriter writer = new IndexWriter(directory, config);
			
			Document doc = new Document();
			//模拟长方形
			doc.add(new IntField("width", 3,Field.Store.YES));
			doc.add(new IntField("longth", 4,Field.Store.YES));
			doc.add(new NumericDocValuesField("width", 3));
			doc.add(new NumericDocValuesField("longth", 4));
			writer.addDocument(doc);
			
			Document doc1 = new Document();
			doc1.add(new IntField("width", 2,Field.Store.YES));
			doc1.add(new IntField("longth", 5,Field.Store.YES));
			doc1.add(new NumericDocValuesField("width", 2));
			doc1.add(new NumericDocValuesField("longth", 5));
			writer.addDocument(doc1);
			
			Document doc2 = new Document();
			doc2.add(new IntField("width", 2,Field.Store.YES));
			doc2.add(new IntField("longth", 6,Field.Store.YES));
			doc2.add(new NumericDocValuesField("width", 2));
			doc2.add(new NumericDocValuesField("longth", 6));
			writer.addDocument(doc2);
			
			writer.commit();
			writer.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/**
	 * 面积比较
	 */
	@Test
	public void testAcreage(){
		try {
			Expression expr = JavascriptCompiler.compile("width*longth");
			
			SimpleBindings bindings = new SimpleBindings();    
			bindings.add(new SortField("width", SortField.Type.INT));
			bindings.add(new SortField("longth", SortField.Type.INT));
			
			Sort sort = new Sort(expr.getSortField(bindings, true));
			Query query = new MatchAllDocsQuery();
			
			Directory directory = FSDirectory.open(Paths.get("index"));
			IndexReader reader = DirectoryReader.open(directory);
			IndexSearcher searcher = new IndexSearcher(reader);
			TopDocs docs = searcher.search(query, 10, sort);
			for (ScoreDoc scoreDoc : docs.scoreDocs) {
				System.out.println(searcher.doc(scoreDoc.doc));
			}
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/**
	 * 周长比较
	 */
	@Test
	public void testCircum(){
		try {
			Expression expr = JavascriptCompiler.compile("width+longth+sqrt(pow(width,2)+pow(longth,2))");
			
			SimpleBindings bindings = new SimpleBindings();    
			bindings.add(new SortField("width", SortField.Type.INT));
			bindings.add(new SortField("longth", SortField.Type.INT));
			
			Sort sort = new Sort(expr.getSortField(bindings, true));
			Query query = new MatchAllDocsQuery();
			
			Directory directory = FSDirectory.open(Paths.get("index"));
			IndexReader reader = DirectoryReader.open(directory);
			IndexSearcher searcher = new IndexSearcher(reader);
			TopDocs docs = searcher.search(query, 10, sort);
			for (ScoreDoc scoreDoc : docs.scoreDocs) {
				System.out.println(searcher.doc(scoreDoc.doc));
			}
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

面积的比较运行结果为：

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Document<stored<width:3> stored<longth:4>>
Document<stored<width:2> stored<longth:6>>
Document<stored<width:2> stored<longth:5>>

同样的，周长比较的运行结果为：

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Document<stored<width:2> stored<longth:6>>
Document<stored<width:2> stored<longth:5>>
Document<stored<width:3> stored<longth:4>>

以上是lucene的expression的应用,源代码下载地址：

http://download.csdn.net/detail/wuyinggui10000/8762423

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