| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.apache.solr.search.similarities; |
| |
| import org.apache.lucene.search.similarities.BM25Similarity; |
| import org.apache.lucene.search.similarities.Similarity; |
| import org.apache.solr.common.params.SolrParams; |
| import org.apache.solr.schema.SimilarityFactory; |
| |
| /** |
| * Factory for BM25Similarity. This is the default similarity since 8.x. |
| * If you need the exact same formula as in 6.x and 7.x you should instead look at |
| * {@link LegacyBM25SimilarityFactory} |
| * <p> |
| * Parameters: |
| * <ul> |
| * <li>k1 (float): Controls non-linear term frequency normalization (saturation). |
| * The default is <code>1.2</code> |
| * <li>b (float): Controls to what degree document length normalizes tf values. |
| * The default is <code>0.75</code> |
| * </ul> |
| * <p> |
| * Optional settings: |
| * <ul> |
| * <li>discountOverlaps (bool): Sets |
| * {@link BM25Similarity#setDiscountOverlaps(boolean)}</li> |
| * </ul> |
| * @lucene.experimental |
| * @since 8.0.0 |
| */ |
| public class BM25SimilarityFactory extends SimilarityFactory { |
| private boolean discountOverlaps; |
| private float k1; |
| private float b; |
| |
| @Override |
| public void init(SolrParams params) { |
| super.init(params); |
| discountOverlaps = params.getBool("discountOverlaps", true); |
| k1 = params.getFloat("k1", 1.2f); |
| b = params.getFloat("b", 0.75f); |
| } |
| |
| @Override |
| public Similarity getSimilarity() { |
| BM25Similarity sim = new BM25Similarity(k1, b); |
| sim.setDiscountOverlaps(discountOverlaps); |
| return sim; |
| } |
| } |