SparseSegmentDataset


1   /*
2   // $Id: //open/mondrian/src/main/mondrian/rolap/agg/SparseSegmentDataset.java#9 $
3   // This software is subject to the terms of the Common Public License
4   // Agreement, available at the following URL:
5   // http://www.opensource.org/licenses/cpl.html.
6   // Copyright (C) 2002-2002 Kana Software, Inc.
7   // Copyright (C) 2002-2007 Julian Hyde and others
8   // All Rights Reserved.
9   // You must accept the terms of that agreement to use this software.
10  //
11  // jhyde, 21 March, 2002
12  */
13  package mondrian.rolap.agg;
14  
15  import mondrian.olap.Util;
16  import mondrian.rolap.CellKey;
17  
18  import java.util.Map  ;
19  import java.util.HashMap  ;
20  import java.util.Iterator  ;
21  
22  /**
23   * A <code>SparseSegmentDataset</code> is a means of storing segment values
24   * which is suitable when few of the combinations of keys have a value present.
25   *
26   * <p>The storage requirements are as follows. Key is 1 word for each
27   * dimension. Hashtable entry is 3 words. Value is 1 word. Total space is (4 +
28   * d) * v. (May also need hash table to ensure that values are only stored
29   * once.)</p>
30   *
31   * <p>NOTE: This class is not synchronized.</p>
32   *
33   * @author jhyde
34   * @since 21 March, 2002
35   * @version $Id: //open/mondrian/src/main/mondrian/rolap/agg/SparseSegmentDataset.java#9 $
36   */
37  class SparseSegmentDataset implements SegmentDataset {
38      private final Map  <CellKey, Object  > values = new HashMap  <CellKey, Object  >();
39  
40      SparseSegmentDataset(Segment segment) {
41          Util.discard(segment);
42      }
43  
44      public Object   get(CellKey pos) {
45          return values.get(pos);
46      }
47  
48      public void put(CellKey key, Object   value) {
49          values.put(key, value);
50      }
51  
52      public Iterator  <Map.Entry  <CellKey, Object  >> iterator() {
53          return values.entrySet().iterator();
54      }
55  
56      public double getBytes() {
57          // assume a slot, key, and value are each 4 bytes
58          return values.size() * 12;
59      }
60  }
61  
62  // End SparseSegmentDataset.java
63
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