Lucene学习--索引的建立
本篇目录：
1.索引建立的步骤
2.域的存储选项和索引选项
3.索引的增删查改
4.IndexReader的单例模式
5.域为数字和日期时的处理
6.生命周期
1.索引建立的步骤
建立索引就是为了在检索时从索引文件中进行快速查找。
各种类型的文件都需要先转换为文本，然后再通过适当的分词器，建立索引文件。
先创建Directory和IndexWriter，然后创建文档Document，之后为文档添加域Field，域的存储选项Field.Store和索引选项Field.Index均需要设置；
文档相当于表中的每一条记录，域相当于表中的每一个字段。
最后通过IndexWriter将文档添加到索引中；
2.域的存储选项和索引选项
被存储———便于对文本进行还原；当Field.Store设为YES时可调用docment.get方法获取该域的完整内容；
被索引———便于通过该域的值检索到所在的文档
在被索引的基础上，又有两个子选项：是否分词、是否加权
是否分词——考量一个域值是否为原子单位，是否允许通过拆分后的片段来检索它；
是否加权——考量是否允许该域值来影响检索到的结果集的顺序；
索引域选项：Field.Index
|
Field.Index的值
|
是否索引
|
是否分词
|
是否加权
|
|
NO
|
X
|
|
|
|
NOT_ANALYZED_NO_NORMS
|
V
|
X
|
X
|
|
ANALYZED
|
V
|
V
|
V
|
|
ANALYZED_NO_NORMS
|
V
|
V
|
X
|
|
NOT_ANALYZED
|
V
|
X
|
V
|
这里存在有最佳实践。
3.索引的增删查改
参加网络视频，好像授课者是一位大学老师。直接粘在这里，以备查用。
0、查询索引的基本信息：
通过IndexReader加载索引文件就可以直接获取文档的数量了（numDoc和maxDoc）
1、删除
2、恢复删除
3、强制删除
4、优化和合并索引
5、更新索引
package org.itat.index;
import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.NumericField;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.StaleReaderException;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.LockObtainFailedException;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.Version;
public class IndexUtil {
private String[] ids = {"1","2","3","4","5","6"};
private String[] emails = {"[email protected]","[email protected]","[email protected]","[email protected]","[email protected]","[email protected]"};
private String[] contents = {
"welcome to visited the space,I like book",
"hello boy, I like pingpeng ball",
"my name is cc I like game",
"I like football",
"I like football and I like basketball too",
"I like movie and swim"
};
private Date[] dates = null;
private int[] attachs = {2,3,1,4,5,5};
private String[] names = {"zhangsan","lisi","john","jetty","mike","jake"};
private Directory directory = null;
private Map<String,Float> scores = new HashMap<String,Float>();
private static IndexReader reader = null;
public IndexUtil() {
try {
setDates();
scores.put("itat.org",2.0f);
scores.put("zttc.edu", 1.5f);
//directory = FSDirectory.open(new File("d:/lucene/index02"));
directory = new RAMDirectory();
index();
reader = IndexReader.open(directory,false);
} catch (IOException e) {
e.printStackTrace();
}
}
public IndexSearcher getSearcher() {
try {
if(reader==null) {
reader = IndexReader.open(directory,false);
} else {
IndexReader tr = IndexReader.openIfChanged(reader);
if(tr!=null) {
reader.close();
reader = tr;
}
}
return new IndexSearcher(reader);
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private void setDates() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
try {
dates = new Date[ids.length];
dates[0] = sdf.parse("2010-02-19");
dates[1] = sdf.parse("2012-01-11");
dates[2] = sdf.parse("2011-09-19");
dates[3] = sdf.parse("2010-12-22");
dates[4] = sdf.parse("2012-01-01");
dates[5] = sdf.parse("2011-05-19");
} catch (ParseException e) {
e.printStackTrace();
}
}
public void undelete() {
//使用IndexReader进行恢复
try {
IndexReader reader = IndexReader.open(directory,false);
//恢复时，必须把IndexReader的只读(readOnly)设置为false
reader.undeleteAll();
reader.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (StaleReaderException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void merge() {
IndexWriter writer = null;
try {
writer = new IndexWriter(directory,
new IndexWriterConfig(Version.LUCENE_35,new StandardAnalyzer(Version.LUCENE_35)));
//会将索引合并为2段，这两段中的被删除的数据会被清空
//特别注意：此处Lucene在3.5之后不建议使用，因为会消耗大量的开销，
//Lucene会根据情况自动处理的
writer.forceMerge(2);
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer!=null) writer.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void forceDelete() {
IndexWriter writer = null;
try {
writer = new IndexWriter(directory,
new IndexWriterConfig(Version.LUCENE_35,new StandardAnalyzer(Version.LUCENE_35)));
writer.forceMergeDeletes();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer!=null) writer.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void delete() {
IndexWriter writer = null;
try {
writer = new IndexWriter(directory,
new IndexWriterConfig(Version.LUCENE_35,new StandardAnalyzer(Version.LUCENE_35)));
//参数是一个选项，可以是一个Query，也可以是一个term，term是一个精确查找的值
//此时删除的文档并不会被完全删除，而是存储在一个回收站中的，可以恢复
writer.deleteDocuments(new Term("id","1"));
writer.commit();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer!=null) writer.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void delete02() {
try {
reader.deleteDocuments(new Term("id","1"));
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void update() {
IndexWriter writer = null;
try {
writer = new IndexWriter(directory,
new IndexWriterConfig(Version.LUCENE_35,new StandardAnalyzer(Version.LUCENE_35)));
/*
* Lucene并没有提供更新，这里的更新操作其实是如下两个操作的合集
* 先删除之后再添加
*/
Document doc = new Document();
doc.add(new Field("id","11",Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
doc.add(new Field("email",emails[0],Field.Store.YES,Field.Index.NOT_ANALYZED));
doc.add(new Field("content",contents[0],Field.Store.NO,Field.Index.ANALYZED));
doc.add(new Field("name",names[0],Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
writer.updateDocument(new Term("id","1"), doc);
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer!=null) writer.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void query() {
try {
IndexReader reader = IndexReader.open(directory);
//通过reader可以有效的获取到文档的数量
System.out.println("numDocs:"+reader.numDocs());
System.out.println("maxDocs:"+reader.maxDoc());
System.out.println("deleteDocs:"+reader.numDeletedDocs());
reader.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void index() {
IndexWriter writer = null;
try {
writer = new IndexWriter(directory, new IndexWriterConfig(Version.LUCENE_35, new StandardAnalyzer(Version.LUCENE_35)));
writer.deleteAll();
Document doc = null;
for(int i=0;i<ids.length;i++) {
doc = new Document();
doc.add(new Field("id",ids[i],Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
doc.add(new Field("email",emails[i],Field.Store.YES,Field.Index.NOT_ANALYZED));
doc.add(new Field("email","test"+i+"@test.com",Field.Store.YES,Field.Index.NOT_ANALYZED));
doc.add(new Field("content",contents[i],Field.Store.NO,Field.Index.ANALYZED));
doc.add(new Field("name",names[i],Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
//存储数字
doc.add(new NumericField("attach",Field.Store.YES,true).setIntValue(attachs[i]));
//存储日期
doc.add(new NumericField("date",Field.Store.YES,true).setLongValue(dates[i].getTime()));
String et = emails[i].substring(emails[i].lastIndexOf("@")+1);
System.out.println(et);
if(scores.containsKey(et)) {
doc.setBoost(scores.get(et));
} else {
doc.setBoost(0.5f);
}
writer.addDocument(doc);
}
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (LockObtainFailedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer!=null)writer.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void search01() {
try {
IndexReader reader = IndexReader.open(directory);
IndexSearcher searcher = new IndexSearcher(reader);
TermQuery query = new TermQuery(new Term("email","[email protected]"));
TopDocs tds = searcher.search(query, 10);
for(ScoreDoc sd:tds.scoreDocs) {
Document doc = searcher.doc(sd.doc);
System.out.println("("+sd.doc+"-"+doc.getBoost()+"-"+sd.score+")"+
doc.get("name")+"["+doc.get("email")+"]-->"+doc.get("id")+","+
doc.get("attach")+","+doc.get("date")+","+doc.getValues("email")[1]);
}
reader.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void search02() {
try {
IndexSearcher searcher = getSearcher();
TermQuery query = new TermQuery(new Term("content","like"));
TopDocs tds = searcher.search(query, 10);
for(ScoreDoc sd:tds.scoreDocs) {
Document doc = searcher.doc(sd.doc);
System.out.println(doc.get("id")+"---->"+
doc.get("name")+"["+doc.get("email")+"]-->"+doc.get("id")+","+
doc.get("attach")+","+doc.get("date")+","+doc.getValues("email")[1]);
}
searcher.close();
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
4.IndexReader的单例模式
public IndexSearcher getSearcher() {
try {
if(reader==null) {
reader = IndexReader.open(directory,false);
} else {
IndexReader tr = IndexReader.openIfChanged(reader);
if(tr!=null) {
reader.close();
reader = tr;
}
}
return new IndexSearcher(reader);
} catch (CorruptIndexException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
5.域为数字和日期时的处理
//存储数字
doc.add(new NumericField("attach",Field.Store.YES,true).setIntValue(attachs[i]));
//存储日期
doc.add(new NumericField("date",Field.Store.YES,true).setLongValue(dates[i].getTime()));
6.IndexReader的生命周期
对于IndexReader而言，之所以使用单例模式，是因为反复使用IndexReader.open打开会有很大的开销，所以一般在整个程序的生命周期中只会打开一个IndexReader,通过这个IndexReader来创建不同的IndexSearcher。
但如果使用单例模式，可能出现的问题有：
1、如果IndexWriter在创建完成之后，没有关闭，需要进行commit操作之后才能提交，才会更新索引文件；
2、当使用IndexWriter修改了索引之后，IndexReader不会自动更新它加载过的索引信息，所以需要使用IndexReader.openIfChange方法操作。