01: /* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com
02:
03: This file is part of the db4o open source object database.
04:
05: db4o is free software; you can redistribute it and/or modify it under
06: the terms of version 2 of the GNU General Public License as published
07: by the Free Software Foundation and as clarified by db4objects' GPL
08: interpretation policy, available at
09: 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.internal.fieldindex;
22:
23: import com.db4o.foundation.*;
24: import com.db4o.internal.query.processor.*;
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: }
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