權值

【概述】

在數學領域，權值指加權平均數中的每個數的頻數，也稱為權數或權重。在搜索引擎中，權值越高的內容在排序中越靠前。

實際應用中可以通過修改權值來重新調整索引在列表中的排序位置。

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【示例】

    /**
     * 創建索引
     */
    @Test
    public void testIndex(){
        //存儲3篇文章的信息。包括：id、標題、作者、內容
        int[] ids = {1,2,3};
        String[] titles = {"Hello","I love you","morning"};
        String[] authors = {"Hello Mike","HanMeimei","Tom"};
        String[] contents= {"Hello,My Name Is Mike; good","Tome,I Love You; good，good,good","Good Moring,I'm so sorry; good,，good,good，good,good"};
        
        IndexWriter writer = null;
        
        try {
            //1、創建Directory
            Directory directory = FSDirectory.open(new File("E:\\lucene\\index2"));
            
            //2、創建Writer
            ......
            
            for(int i = 0;i<ids.length;i++){
                doc = new Document();
                
                //為文檔添加域(屬性)
                String id = Integer.toString(ids[i]);
                doc.add(new Field("id",id,Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
                doc.add(new Field("title",titles[i],Field.Store.YES,Field.Index.NOT_ANALYZED));
                doc.add(new Field("author",authors[i],Field.Store.YES,Field.Index.NOT_ANALYZED));
                doc.add(new Field("content", contents[i],Field.Store.NO,Field.Index.ANALYZED));
                
                //修改索引的權值
                //默認權值為1.0
                //將Id為1的數據權值調整到5.0
                if(ids[i] == 1)
                    doc.setBoost(5.0f);
                
                writer.addDocument(doc);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        finally{
            if(writer != null)
                try {
                    writer.close();
                } catch (CorruptIndexException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
        }
    }

注意：讀取索引時讀取到的權值和索引中的權值是不同的。因為他們屬于不同的doc對象。