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/* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com */
using System.Collections;
using Db4objects.Db4o.Internal.Fieldindex;
using Db4objects.Db4o.Internal.Query.Processor;
namespace Db4objects.Db4o.Internal.Fieldindex
{
public class FieldIndexProcessor
{
private readonly QCandidates _candidates;
public FieldIndexProcessor(QCandidates candidates)
{
_candidates = candidates;
}
public virtual FieldIndexProcessorResult Run()
{
IIndexedNode bestIndex = SelectBestIndex();
if (null == bestIndex)
{
return FieldIndexProcessorResult.NO_INDEX_FOUND;
}
if (bestIndex.ResultSize() > 0)
{
IIndexedNode resolved = ResolveFully(bestIndex);
if (null == resolved)
{
return FieldIndexProcessorResult.NO_INDEX_FOUND;
}
return new FieldIndexProcessorResult(resolved);
}
return FieldIndexProcessorResult.FOUND_INDEX_BUT_NO_MATCH;
}
private IIndexedNode ResolveFully(IIndexedNode bestIndex)
{
if (null == bestIndex)
{
return null;
}
if (bestIndex.IsResolved())
{
return bestIndex;
}
return ResolveFully(bestIndex.Resolve());
}
public virtual IIndexedNode SelectBestIndex()
{
IEnumerator i = CollectIndexedNodes();
if (!i.MoveNext())
{
return null;
}
IIndexedNode best = (IIndexedNode)i.Current;
while (i.MoveNext())
{
IIndexedNode leaf = (IIndexedNode)i.Current;
if (leaf.ResultSize() < best.ResultSize())
{
best = leaf;
}
}
return best;
}
public virtual IEnumerator CollectIndexedNodes()
{
return new IndexedNodeCollector(_candidates).GetNodes();
}
}
}
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