/**
* Copyright 2014 National University of Ireland, Galway.
*
* This file is part of the SIREn project. Project and contact information:
*
* https://github.com/rdelbru/SIREn
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.sindice.siren.search.node;
import java.io.IOException;
import java.util.Comparator;
import org.apache.lucene.index.AtomicReaderContext;
import org.apache.lucene.index.Fields;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexReaderContext;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermContext;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.BytesRef;
import org.sindice.siren.search.node.MultiNodeTermQuery.RewriteMethod;
/**
* Abstract class for rewrite methods.
*
* <p>
*
* Code taken from {@link TermCollectingRewrite} and adapted for SIREn.
*/
abstract class NodeTermCollectingRewrite<Q extends Query> extends RewriteMethod {
/** Return a suitable top-level Query for holding all expanded terms. */
protected abstract Q getTopLevelQuery() throws IOException;
/** Add a MultiTermQuery term to the top-level query */
protected final void addClause(final Q topLevel, final Term term, final int docCount, final float boost)
throws IOException {
this.addClause(topLevel, term, docCount, boost, null);
}
protected abstract void addClause(Q topLevel, Term term, int docCount,
float boost, TermContext states)
throws IOException;
final void collectTerms(final IndexReader reader,
final MultiNodeTermQuery query,
final TermCollector collector)
throws IOException {
final IndexReaderContext topReaderContext = reader.getContext();
Comparator<BytesRef> lastTermComp = null;
for (final AtomicReaderContext context : topReaderContext.leaves()) {
final Fields fields = context.reader().fields();
if (fields == null) {
// reader has no fields
continue;
}
final Terms terms = fields.terms(query.field);
if (terms == null) {
// field does not exist
continue;
}
final TermsEnum termsEnum = this.getTermsEnum(query, terms, collector.attributes);
assert termsEnum != null;
if (termsEnum == TermsEnum.EMPTY)
continue;
// Check comparator compatibility:
final Comparator<BytesRef> newTermComp = termsEnum.getComparator();
if (lastTermComp != null && newTermComp != null && newTermComp != lastTermComp)
throw new RuntimeException("term comparator should not change between segments: "+lastTermComp+" != "+newTermComp);
lastTermComp = newTermComp;
collector.setReaderContext(topReaderContext, context);
collector.setNextEnum(termsEnum);
BytesRef bytes;
while ((bytes = termsEnum.next()) != null) {
if (!collector.collect(bytes))
return; // interrupt whole term collection, so also don't iterate other subReaders
}
}
}
static abstract class TermCollector
{
protected AtomicReaderContext readerContext;
protected IndexReaderContext topReaderContext;
public void setReaderContext(final IndexReaderContext topReaderContext,
final AtomicReaderContext readerContext) {
this.readerContext = readerContext;
this.topReaderContext = topReaderContext;
}
/** attributes used for communication with the enum */
public final AttributeSource attributes = new AttributeSource();
/** return false to stop collecting */
public abstract boolean collect(BytesRef bytes) throws IOException;
/** the next segment's {@link TermsEnum} that is used to collect terms */
public abstract void setNextEnum(TermsEnum termsEnum) throws IOException;
}
}