LUCENE-6304: Add MatchNoDocsQuery.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1663899 13f79535-47bb-0310-9956-ffa450edef68

lucene/CHANGES.txt

@@ -54,6 +54,9 @@ New Features
 * LUCENE-6303: Added filter caching baked into IndexSearcher and enabled by
   default. (Adrien Grand)
 
+* LUCENE-6304: Added a new MatchNoDocsQuery that matches no documents.
+  (Lee Hinman via Adrien Grand)
+
 Bug Fixes
 
 * LUCENE-6249: StandardQueryParser doesn't support pure negative clauses. 

lucene/core/src/java/org/apache/lucene/search/MatchNoDocsQuery.java

@@ -0,0 +1,47 @@
+package org.apache.lucene.search;
+
+/*
+ * 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 java.io.IOException;
+import java.util.Set;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.ToStringUtils;
+
+/**
+ * A query that matches no documents.
+ */
+public class MatchNoDocsQuery extends Query {
+
+    @Override
+    public Query rewrite(IndexReader reader) throws IOException {
+        // Rewrite to an empty BooleanQuery so no Scorer or Weight is required
+        return new BooleanQuery();
+    }
+
+    @Override
+    public String toString(String field) {
+        StringBuilder buffer = new StringBuilder();
+        buffer.append("_none_");
+        buffer.append(ToStringUtils.boost(getBoost()));
+        return buffer.toString();
+    }
+}

lucene/core/src/java/org/apache/lucene/search/Query.java

@@ -112,10 +112,7 @@ public abstract class Query implements Cloneable {
 
   @Override
   public int hashCode() {
-    final int prime = 31;
-    int result = 1;
-    result = prime * result + Float.floatToIntBits(boost);
-    return result;
+    return Float.floatToIntBits(getBoost()) ^ getClass().hashCode();
   }
 
   @Override

lucene/core/src/test/org/apache/lucene/search/TestMatchNoDocsQuery.java

@@ -0,0 +1,86 @@
+/*
+ * 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.lucene.search;
+
+import java.io.IOException;
+
+import org.apache.lucene.analysis.Analyzer;
+import org.apache.lucene.analysis.MockAnalyzer;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.store.Directory;
+
+import org.apache.lucene.util.LuceneTestCase;
+
+/**
+ * Tests MatchNoDocsQuery.
+ */
+public class TestMatchNoDocsQuery extends LuceneTestCase {
+  private Analyzer analyzer;
+
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+    analyzer = new MockAnalyzer(random());
+  }
+
+  public void testQuery() throws Exception {
+    Directory dir = newDirectory();
+    IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig(analyzer).setMaxBufferedDocs(2).setMergePolicy(newLogMergePolicy()));
+    addDoc("one", iw);
+    addDoc("two", iw);
+    addDoc("three four", iw);
+    IndexReader ir = DirectoryReader.open(iw, true);
+
+    IndexSearcher is = newSearcher(ir);
+    ScoreDoc[] hits;
+
+    hits = is.search(new MatchNoDocsQuery(), 1000).scoreDocs;
+    assertEquals(0, hits.length);
+
+    // A MatchNoDocsQuery rewrites to an empty BooleanQuery
+    MatchNoDocsQuery mndq = new MatchNoDocsQuery();
+    Query rewritten = mndq.rewrite(ir);
+    assertTrue(rewritten instanceof BooleanQuery);
+    assertEquals(0, ((BooleanQuery) rewritten).clauses().size());
+    hits = is.search(mndq, 1000).scoreDocs;
+    assertEquals(0, hits.length);
+
+    iw.close();
+    ir.close();
+    dir.close();
+  }
+
+  public void testEquals() {
+    Query q1 = new MatchNoDocsQuery();
+    Query q2 = new MatchNoDocsQuery();
+    assertTrue(q1.equals(q2));
+    QueryUtils.check(q1);
+  }
+
+  private void addDoc(String text, IndexWriter iw) throws IOException {
+    Document doc = new Document();
+    Field f = newTextField("key", text, Field.Store.YES);
+    doc.add(f);
+    iw.addDocument(doc);
+  }
+
+}

lucene/queryparser/src/java/org/apache/lucene/queryparser/simple/SimpleQueryParser.java

@@ -23,6 +23,7 @@ import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.FuzzyQuery;
 import org.apache.lucene.search.MatchAllDocsQuery;
+import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.PrefixQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.util.QueryBuilder;
@@ -149,7 +150,7 @@ public class SimpleQueryParser extends QueryBuilder {
     State state = new State(data, buffer, 0, data.length);
     parseSubQuery(state);
     if (state.top == null) {
-      return new BooleanQuery();
+      return new MatchNoDocsQuery();
     } else {
       return state.top;
     }

lucene/queryparser/src/test/org/apache/lucene/queryparser/simple/TestSimpleQueryParser.java

@@ -29,6 +29,7 @@ import org.apache.lucene.search.BooleanClause.Occur;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.FuzzyQuery;
 import org.apache.lucene.search.MatchAllDocsQuery;
+import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.PhraseQuery;
 import org.apache.lucene.search.PrefixQuery;
 import org.apache.lucene.search.Query;
@@ -273,7 +274,7 @@ public class TestSimpleQueryParser extends LuceneTestCase {
   }
 
   public void testGarbageEmpty() throws Exception {
-    BooleanQuery expected = new BooleanQuery();
+    MatchNoDocsQuery expected = new MatchNoDocsQuery();
 
     assertEquals(expected, parse(""));
     assertEquals(expected, parse("  "));