在Lucene.net实现自定义排序

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

public   interface  SortComparatorSource
{
   ScoreDocComparator NewComparator(IndexReader reader , System.String fieldname) ;
}

public   interface  ScoreDocComparator
{
    int  Compare(ScoreDoc i , ScoreDoc j) ;
   System.IComparable SortValue(ScoreDoc i) ;
    int  SortType() ;
}

 

涉及到的一个类：

public   class  ScoreDoc
{
    public   float  score ;
    public   int  doc ;
    public  ScoreDoc( int  doc ,  float  score)
   {
       this .doc  =  doc ;
       this .score  =  score ;
   }
}

 

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:
     public   class  DateDocComparator : Lucene.Net.Search.ScoreDocComparator 
    {
         private   string  fieldname  =   null ;
         private  System.IComparable[] cachedValues ;

         public  DateDocComparator(System.IComparable[] cachedValues,  string  fieldname)
        {
             this .cachedValues  =  cachedValues;
             this .fieldname  =   string .Intern(fieldname) ;
        }

         public   int  Compare(ScoreDoc i, ScoreDoc j)
        {
             return   this .cachedValues[i.doc].CompareTo( this .cachedValues[j.doc]) ;
        }

         public  System.IComparable SortValue(ScoreDoc i)
        {
             return   this .cachedValues[i.doc] ;
        }

         public   int  SortType()
        {
             return  Lucene.Net.Search.SortField.CUSTOM ;
        }
    }

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

  public   class  DateSortComparatorSource : Lucene.Net.Search.SortComparatorSource
    {
         public  ScoreDocComparator NewComparator(Lucene.Net.Index.IndexReader reader, System.String field)
        {
             return   new  DateDocComparator(GetCustom(reader, field), field);
        }

         protected   virtual  System.IComparable[] GetCustom(Lucene.Net.Index.IndexReader reader, System.String field)
        {
                System.IComparable[] retArray  =   new  System.IComparable[reader.MaxDoc()];
                Lucene.Net.Index.TermDocs termDocs  =  reader.TermDocs();
                Lucene.Net.Index.TermEnum termEnum  =  reader.Terms( new  Lucene.Net.Index.Term(field,  "" ));
                 try
                {
                     do
                    {
                        Lucene.Net.Index.Term term  =  termEnum.Term();
                         if  (term  ==   null   ||  term.Field()  !=  field)
                             break ;
                        System.IComparable termval  =  Lucene.Net.Documents.DateTools.StringToDate(term.Text()) ;
                        termDocs.Seek(termEnum);
                         while  (termDocs.Next())
                        {
                            retArray[termDocs.Doc()]  =  termval;
                        }
                    }
                     while  (termEnum.Next());
                }
                 finally
                {
                    termDocs.Close();
                    termEnum.Close();
                }
                 return  retArray;
        }
    }

   

使用：

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