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Java > Open Source Codes > com > db4o > inside > fieldindex > FieldIndexProcessor


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.inside.fieldindex;
22
23 import com.db4o.*;
24 import com.db4o.foundation.*;
25
26 public class FieldIndexProcessor {
27
28     private final QCandidates _candidates;
29
30     public FieldIndexProcessor(QCandidates candidates) {
31         _candidates = candidates;
32     }
33     
34     public FieldIndexProcessorResult run() {
35         IndexedNode bestIndex = selectBestIndex();
36         if (null == bestIndex) {
37             return FieldIndexProcessorResult.NO_INDEX_FOUND;
38         }
39         if (bestIndex.resultSize() > 0) {
40             IndexedNode resolved = resolveFully(bestIndex);
41             if (null == resolved) {
42                 return FieldIndexProcessorResult.NO_INDEX_FOUND;
43             }
44             return new FieldIndexProcessorResult(resolved);
45         }
46         return FieldIndexProcessorResult.FOUND_INDEX_BUT_NO_MATCH;
47     }
48
49     private IndexedNode resolveFully(IndexedNode bestIndex) {
50         if (null == bestIndex) {
51             return null;
52         }
53         if (bestIndex.isResolved()) {
54             return bestIndex;
55         }
56         return resolveFully(bestIndex.resolve());
57     }
58     
59     public IndexedNode selectBestIndex() {
60         final Iterator4 i = collectIndexedNodes();
61         if (!i.moveNext()) {
62             return null;
63         }
64         
65         IndexedNode best = (IndexedNode)i.current();
66         while (i.moveNext()) {
67             IndexedNode leaf = (IndexedNode)i.current();
68             if (leaf.resultSize() < best.resultSize()) {
69                 best = leaf;
70             }
71         }
72         return best;
73     }
74
75     public Iterator4 collectIndexedNodes() {
76         return new IndexedNodeCollector(_candidates).getNodes();
77     }
78 }
79
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