（转）Lucene.net实现自定义排序

本文转自：http://www.cnblogs.com/peida/archive/2008/11/27/1341920.html

在Lucene.net实现自定义排序，需要实现两个Lucene.Net.Search的两个接口：

 1 public interface SortComparatorSource
 2 {
 3    ScoreDocComparator NewComparator(IndexReader reader , System.String fieldname) ;
 4 }
 5 
 6 public interface ScoreDocComparator
 7 {
 8    int Compare(ScoreDoc i , ScoreDoc j) ;
 9    System.IComparable SortValue(ScoreDoc i) ;
10    int SortType() ;
11 }

涉及到的一个类：

 1 public class ScoreDoc
 2 {
 3    public float score ;
 4    public int doc ;
 5    public ScoreDoc(int doc , float score)
 6    {
 7       this.doc = doc ;
 8       this.score = score ;
 9    }
10 }

Lucene.net 2.0包含的SortType有：
在Lucene.Net.Search.SortField里定义的：

public class SortField
{
   public const int SCORE = 0 ;  //相关度
   public const int DOC = 1 ;    //文挡号
   public const int AUTO = 2 ;   //自动识别
   public const int STRING = 3 ; //字符型
   public const int INT = 4 ;    //int
   public const int FLOAT = 5 ;  //float
   public const int CUSTOM = 9 ; //自定义
   ..
}

少了DateTime,那就实现DateTime类型的自定义排序来测试下：
Lucene.Net.Search.ScoreDocComparator接口的实现类:

 1     public class DateDocComparator : Lucene.Net.Search.ScoreDocComparator 
 2     {
 3         private string fieldname = null;
 4         private System.IComparable[] cachedValues ;
 5 
 6         public DateDocComparator(System.IComparable[] cachedValues, string fieldname)
 7         {
 8             this.cachedValues = cachedValues;
 9             this.fieldname = string.Intern(fieldname) ;
10         }
11 
12         public int Compare(ScoreDoc i, ScoreDoc j)
13         {
14             return this.cachedValues[i.doc].CompareTo(this.cachedValues[j.doc]) ;
15         }
16 
17         public System.IComparable SortValue(ScoreDoc i)
18         {
19             return this.cachedValues[i.doc] ;
20         }
21 
22         public int SortType()
23         {
24             return Lucene.Net.Search.SortField.CUSTOM ;
25         }
26     }

Lucene.Net.Search.SortComparatorSource接口的实现类:

 1 public class DateSortComparatorSource : Lucene.Net.Search.SortComparatorSource
 2     {
 3         public ScoreDocComparator NewComparator(Lucene.Net.Index.IndexReader reader, System.String field)
 4         {
 5             return new DateDocComparator(GetCustom(reader, field), field);
 6         }
 7 
 8         protected virtual System.IComparable[] GetCustom(Lucene.Net.Index.IndexReader reader, System.String field)
 9         {
10                 System.IComparable[] retArray = new System.IComparable[reader.MaxDoc()];
11                 Lucene.Net.Index.TermDocs termDocs = reader.TermDocs();
12                 Lucene.Net.Index.TermEnum termEnum = reader.Terms(new Lucene.Net.Index.Term(field, ""));
13                 try
14                 {
15                     do
16                     {
17                         Lucene.Net.Index.Term term = termEnum.Term();
18                         if (term == null || term.Field() != field)
19                             break;
20                         System.IComparable termval = Lucene.Net.Documents.DateTools.StringToDate(term.Text()) ;
21                         termDocs.Seek(termEnum);
22                         while (termDocs.Next())
23                         {
24                             retArray[termDocs.Doc()] = termval;
25                         }
26                     }
27                     while (termEnum.Next());
28                 }
29                 finally
30                 {
31                     termDocs.Close();
32                     termEnum.Close();
33                 }
34                 return retArray;
35         }
36     }

使用：

1 Sort sort = new Sort(new SortField("datecreated",new DateSortComparatorSource(),true)) ;