/* This file is part of the db4o object database http://www.db4o.com
Copyright (C) 2004 - 2011 Versant Corporation http://www.versant.com
db4o is free software; you can redistribute it and/or modify it under
the terms of version 3 of the GNU General Public License as published
by the Free Software Foundation.
db4o is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see http://www.gnu.org/licenses/. */
package com.db4o.internal.fieldindex;
import com.db4o.foundation.*;
import com.db4o.internal.query.processor.*;
public class FieldIndexProcessor {
private final QCandidates _candidates;
public FieldIndexProcessor(QCandidates candidates) {
_candidates = candidates;
}
public FieldIndexProcessorResult run() {
IndexedNode bestIndex = selectBestIndex();
if (null == bestIndex) {
return FieldIndexProcessorResult.NO_INDEX_FOUND;
}
IndexedNode resolved = resolveFully(bestIndex);
if (! bestIndex.isEmpty()) {
bestIndex.markAsBestIndex(_candidates);
return new FieldIndexProcessorResult(resolved);
}
return FieldIndexProcessorResult.FOUND_INDEX_BUT_NO_MATCH;
}
private IndexedNode resolveFully(IndexedNode indexedNode) {
if (null == indexedNode) {
return null;
}
if (indexedNode.isResolved()) {
return indexedNode;
}
return resolveFully(indexedNode.resolve());
}
public IndexedNode selectBestIndex() {
final Iterator4 i = collectIndexedNodes();
IndexedNode best = null;
while (i.moveNext()) {
IndexedNode indexedNode = (IndexedNode)i.current();
IndexedNode resolved = resolveFully(indexedNode);
if(resolved == null){
continue;
}
if(best == null){
best = indexedNode;
continue;
}
if (indexedNode.resultSize() < best.resultSize()) {
best = indexedNode;
}
}
return best;
}
public Iterator4 collectIndexedNodes() {
return new IndexedNodeCollector(_candidates).getNodes();
}
}