SOLR-8261: Change SchemaSimilarityFactory default to BM25Similarity

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1713557 13f79535-47bb-0310-9956-ffa450edef68

solr/CHANGES.txt

@@ -55,6 +55,10 @@ Upgrading from Solr 5.x
   refrenced in your schema.xml, edit your config to use the functionally identical ClassicSimilarityFactory.
   See SOLR-8239 for more details.
 
+* SchemaSimilarityFactory has been modified to use BM25Similarity as the default for fieldTypes that
+  do not explicitly declare a Similarity.  The legacy behavior of using ClassicSimilarity as the
+  default will occur if the luceneMatchVersion for the collection is less then 6.0.  See SOLR-8261 for
+  more details.
 
 Detailed Change List
 ----------------------
@@ -130,6 +134,8 @@ Other Changes
 * SOLR-8114: in Grouping.java rename groupSort and sort to withinGroupSort and groupSort
   (Christine Poerschke)
 
+* SOLR-8261: Change SchemaSimilarityFactory default to BM25Similarity (hossman)
+
 ==================  5.4.0 ==================
 
 Consult the LUCENE_CHANGES.txt file for additional, low level, changes in this release

solr/core/src/java/org/apache/solr/search/similarities/SchemaSimilarityFactory.java

@@ -18,8 +18,11 @@ package org.apache.solr.search.similarities;
  */
 
 import org.apache.lucene.search.similarities.ClassicSimilarity;
+import org.apache.lucene.search.similarities.BM25Similarity;
 import org.apache.lucene.search.similarities.PerFieldSimilarityWrapper;
 import org.apache.lucene.search.similarities.Similarity;
+import org.apache.lucene.util.Version;
+
 import org.apache.solr.common.params.SolrParams;
 import org.apache.solr.core.SolrCore;
 import org.apache.solr.schema.FieldType;
@@ -27,10 +30,15 @@ import org.apache.solr.schema.SimilarityFactory;
 import org.apache.solr.util.plugin.SolrCoreAware;
 
 /**
+ * <p>
  * SimilarityFactory that returns a {@link PerFieldSimilarityWrapper}
  * that delegates to the field type, if it's configured, otherwise
- * {@link ClassicSimilarity}.
- *
+ * returns a sensible default depending on the {@link Version} matching configured.
+ * </p>
+ * <ul>
+ *  <li><code>luceneMatchVersion &lt; 6.0</code> = {@link ClassicSimilarity}</li>
+ *  <li><code>luceneMatchVersion &gt;= 6.0</code> = {@link BM25Similarity}</li>
+ * </ul>
  * <p>
  * <b>NOTE:</b> Users should be aware that in addition to supporting 
  * <code>Similarity</code> configurations specified on individual 
@@ -44,13 +52,16 @@ import org.apache.solr.util.plugin.SolrCoreAware;
  * @see FieldType#getSimilarity
  */
 public class SchemaSimilarityFactory extends SimilarityFactory implements SolrCoreAware {
-  private Similarity similarity;
-  private Similarity defaultSimilarity = new ClassicSimilarity();
+  private Similarity similarity; // set by init
+  private Similarity defaultSimilarity; // set by inform(SolrCore)
   private volatile SolrCore core;
 
   @Override
   public void inform(SolrCore core) {
     this.core = core;
+    this.defaultSimilarity = this.core.getSolrConfig().luceneMatchVersion.onOrAfter(Version.LUCENE_6_0_0)
+      ? new BM25Similarity()
+      : new ClassicSimilarity();
   }
   
   @Override

solr/core/src/test/org/apache/solr/search/similarities/TestPerFieldSimilarity.java

@@ -18,12 +18,13 @@ package org.apache.solr.search.similarities;
  */
 
 import org.apache.lucene.misc.SweetSpotSimilarity;
-import org.apache.lucene.search.similarities.ClassicSimilarity;
+import org.apache.lucene.search.similarities.BM25Similarity;
 import org.apache.lucene.search.similarities.Similarity;
 import org.junit.BeforeClass;
 
 /**
  * Tests per-field similarity support in the schema
+ * @see TestPerFieldSimilarityClassic
  */
 public class TestPerFieldSimilarity extends BaseSimilarityTestCase {
 
@@ -59,18 +60,18 @@ public class TestPerFieldSimilarity extends BaseSimilarityTestCase {
   /** test a field where no similarity is specified */
   public void testDefaults() throws Exception {
     Similarity sim = getSimilarity("sim3text");
-    assertEquals(ClassicSimilarity.class, sim.getClass());;
+    assertEquals(BM25Similarity.class, sim.getClass());;
   }
   
   /** ... and for a dynamic field */
   public void testDefaultsDynamic() throws Exception {
     Similarity sim = getSimilarity("text_sim3");
-    assertEquals(ClassicSimilarity.class, sim.getClass());
+    assertEquals(BM25Similarity.class, sim.getClass());
   }
   
   /** test a field that does not exist */
   public void testNonexistent() throws Exception {
     Similarity sim = getSimilarity("sdfdsfdsfdswr5fsdfdsfdsfs");
-    assertEquals(ClassicSimilarity.class, sim.getClass());
+    assertEquals(BM25Similarity.class, sim.getClass());
   }
 }

solr/core/src/test/org/apache/solr/search/similarities/TestPerFieldSimilarityClassic.java

@@ -0,0 +1,87 @@
+package org.apache.solr.search.similarities;
+
+/*
+ * 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.
+ */
+
+import org.apache.lucene.misc.SweetSpotSimilarity;
+import org.apache.lucene.search.similarities.ClassicSimilarity;
+import org.apache.lucene.search.similarities.Similarity;
+import org.apache.lucene.util.Version;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+
+/**
+ * Tests per-field similarity support in the schema when luceneMatchVersion indicates 
+ * {@link ClassicSimilarity} should be the default.
+ * @see TestPerFieldSimilarity
+ */
+public class TestPerFieldSimilarityClassic extends BaseSimilarityTestCase {
+
+  @BeforeClass
+  public static void beforeClass() throws Exception {
+    // any value below 6.0 should have this behavior
+    System.setProperty("tests.luceneMatchVersion", Version.LUCENE_5_3_1.toString());
+    initCore("solrconfig-basic.xml","schema-sim.xml");
+  }
+  
+  @AfterClass
+  public static void afterClass() throws Exception {
+    System.clearProperty("tests.luceneMatchVersion");
+  }
+
+  /** test a field where the sim is specified directly */
+  public void testDirect() throws Exception {
+    assertEquals(SweetSpotSimilarity.class, getSimilarity("sim1text").getClass());
+  }
+  
+  /** ... and for a dynamic field */
+  public void testDirectDynamic() throws Exception {
+    assertEquals(SweetSpotSimilarity.class, getSimilarity("text_sim1").getClass());
+  }
+  
+  /** test a field where a configurable sim factory is defined */
+  public void testFactory() throws Exception {
+    Similarity sim = getSimilarity("sim2text");
+    assertEquals(MockConfigurableSimilarity.class, sim.getClass());
+    assertEquals("is there an echo?", ((MockConfigurableSimilarity)sim).getPassthrough());
+  }
+  
+  /** ... and for a dynamic field */
+  public void testFactoryDynamic() throws Exception {
+    Similarity sim = getSimilarity("text_sim2");
+    assertEquals(MockConfigurableSimilarity.class, sim.getClass());
+    assertEquals("is there an echo?", ((MockConfigurableSimilarity)sim).getPassthrough());
+  }
+  
+  /** test a field where no similarity is specified */
+  public void testDefaults() throws Exception {
+    Similarity sim = getSimilarity("sim3text");
+    assertEquals(ClassicSimilarity.class, sim.getClass());;
+  }
+  
+  /** ... and for a dynamic field */
+  public void testDefaultsDynamic() throws Exception {
+    Similarity sim = getSimilarity("text_sim3");
+    assertEquals(ClassicSimilarity.class, sim.getClass());
+  }
+  
+  /** test a field that does not exist */
+  public void testNonexistent() throws Exception {
+    Similarity sim = getSimilarity("sdfdsfdsfdswr5fsdfdsfdsfs");
+    assertEquals(ClassicSimilarity.class, sim.getClass());
+  }
+}