堡政島

NumericField , 根據官方 API  介紹如下 :

This class provides a Field that enables indexing of numeric values for efficient range filtering and sorting.  

NumericField class 提供一個專門儲存數字的欄位 , 它可以在搜尋數字區間時獲得更好的效果 

The following is sample  : 

document.Add(new NumericField(name).SetIntValue(value));

Step1 : Build RAMDirectory 

        為了減少 code 的量 , 把焦點更集中在 NumericField , 因此使用了 RAMDirectory

 public static RAMDirectory dir = new RAMDirectory();

Step 2 : Build Index 

        在下面建立了 1000項產品 , 包含 PROD_ID [產品ID] , PROD_Name [產品名稱] , PROD_Price [產品價格] , 

        而PROD_Price 是 NumericField , 我們等等要搜尋某個區間的價格出來 

 private void BuildIndex() {

        IndexWriter iw = new IndexWriter(dir, new StandardAnalyzer(Version.LUCENE_30), true, IndexWriter.MaxFieldLength.UNLIMITED);

        for (int i = 1; i <= 1000; i++)
        {
            Document doc = new Document();
            Field field = new Field("PROD_ID", Guid.NewGuid().ToString(), Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.NO);
            Field field2 = new Field("PROD_Name", "Lucene.Net" + i.ToString(), Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.NO);
            NumericField field3 = new NumericField("PROD_Price", Field.Store.YES, true);
            field3.SetIntValue(i);
            doc.Add(field);
            doc.Add(field2);
            doc.Add(field3);
            iw.AddDocument(doc);
        }

        iw.Optimize();
        iw.Commit();
        iw.Close();
    
    }

Step 3 : Search 

        接下來我們要搜尋價格區間在 11 ~ 20 之間的產品出來 , 其程式碼在 Line : 7 , 設置了 11 跟 20 的參數

private void SearchIndex() { 
    
        IndexSearcher search = new IndexSearcher(dir,true);

        QueryParser qp = new QueryParser(Version.LUCENE_30, "PROD_Price", new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_30));
        
        var nq = NumericRangeQuery.NewIntRange("PROD_Price", 11, 20, true, true);

        var hits = search.Search(nq, null, search.MaxDoc).ScoreDocs;

        foreach (var res in hits)
        {
            Response.Write(string.Format("PROD_ID:{0} / PROD_Name{1} / PROD_Price{2}", search.Doc(res.Doc).Get("PROD_ID").ToString()
                                        , search.Doc(res.Doc).Get("PROD_Name").ToString()
                                        , search.Doc(res.Doc).Get("PROD_Price").ToString() + "
"));
        }
    }

Result : 

PROD_ID:563a2d5a-e6ba-4dbd-9276-b7a0a6c81015 / PROD_NameLucene.Net11 / PROD_Price11
PROD_ID:6d5e2353-0b25-4d5b-834e-c243453659f7 / PROD_NameLucene.Net12 / PROD_Price12
PROD_ID:85ab8b54-f779-4f6f-86fb-a1e5f2f1eae6 / PROD_NameLucene.Net13 / PROD_Price13
PROD_ID:652b573e-f7ee-487e-87a1-2aa50882e832 / PROD_NameLucene.Net14 / PROD_Price14
PROD_ID:11d8ba45-db63-4a4f-9454-3f49f8082dcd / PROD_NameLucene.Net15 / PROD_Price15
PROD_ID:19ee84a1-56ec-4754-bd8e-b643fa875f75 / PROD_NameLucene.Net16 / PROD_Price16
PROD_ID:eab7a441-fac8-4020-8eea-62a7c271816e / PROD_NameLucene.Net17 / PROD_Price17
PROD_ID:2fae37b1-3c97-4425-a206-0f29788781b3 / PROD_NameLucene.Net18 / PROD_Price18
PROD_ID:f65da88f-fba9-4e95-a203-2764f2c6125e / PROD_NameLucene.Net19 / PROD_Price19
PROD_ID:9c9f1bf1-07f9-4111-b025-7b06d417826b / PROD_NameLucene.Net20 / PROD_Price20

註記 : 在剛才 Build Index 的部分 , 我們在迴圈中不斷建立 Document 物件 跟 NumericField 其實是不正確的作法 , 

在 Lucene.Net API 文件也提到如下 : 

For optimal  performance, re-use the NumericField and Document instance for more than one document:

private void BuildIndex() {

        IndexWriter iw = new IndexWriter(dir, new StandardAnalyzer(Version.LUCENE_30), true, IndexWriter.MaxFieldLength.UNLIMITED);

        Document doc = new Document();

        doc.Add(new Field("PROD_ID", "", Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.NO));
        doc.Add(new Field("PROD_Name", "", Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.NO));
        NumericField field = new NumericField("PROD_Price", Field.Store.YES, true);

        for (int i = 1; i <= 1000; i++)
        {
            doc.GetField("PROD_ID").SetValue(Guid.NewGuid().ToString());
            doc.GetField("PROD_Name").SetValue("Lucene.Net" + i.ToString());
            field.SetIntValue(i);
            doc.Add(field);
            iw.AddDocument(doc);
        }

        iw.Optimize();
        iw.Commit();
        iw.Close();
    
    }

資料來源 : 

Lucene.Net API