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Elasticsearch subproject :server
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.search.slice;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.PostingsEnum;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.ConstantScoreScorer;
import org.apache.lucene.search.ConstantScoreWeight;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.ScoreMode;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Weight;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.DocIdSetBuilder;
import org.apache.lucene.util.StringHelper;
import java.io.IOException;
/**
* A {@link SliceQuery} that uses the terms dictionary of a field to do the slicing.
*
* NOTE: The cost of this filter is O(N*M) where N is the number of unique terms in the dictionary
* and M is the average number of documents per term.
* For each segment this filter enumerates the terms dictionary, computes the hash code for each term and fills
* a bit set with the documents of all terms whose hash code matches the predicate.
* NOTE: Documents with no value for that field are ignored.
*/
public final class TermsSliceQuery extends SliceQuery {
// Fixed seed for computing term hashCode
public static final int SEED = 7919;
public TermsSliceQuery(String field, int id, int max) {
super(field, id, max);
}
@Override
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException {
return new ConstantScoreWeight(this, boost) {
@Override
public Scorer scorer(LeafReaderContext context) throws IOException {
final DocIdSet disi = build(context.reader());
final DocIdSetIterator leafIt = disi.iterator();
return new ConstantScoreScorer(this, score(), scoreMode, leafIt);
}
@Override
public boolean isCacheable(LeafReaderContext ctx) {
return true;
}
};
}
/**
* Returns a DocIdSet per segments containing the matching docs for the specified slice.
*/
private DocIdSet build(LeafReader reader) throws IOException {
final DocIdSetBuilder builder = new DocIdSetBuilder(reader.maxDoc());
final Terms terms = reader.terms(getField());
if (terms == null) {
return DocIdSet.EMPTY;
}
final TermsEnum te = terms.iterator();
PostingsEnum docsEnum = null;
for (BytesRef term = te.next(); term != null; term = te.next()) {
// use a fixed seed instead of term.hashCode() otherwise this query may return inconsistent results when
// running on another replica (StringHelper sets its default seed at startup with current time)
int hashCode = StringHelper.murmurhash3_x86_32(term, SEED);
if (contains(hashCode)) {
docsEnum = te.postings(docsEnum, PostingsEnum.NONE);
builder.add(docsEnum);
}
}
return builder.build();
}
}