HSEARCH-1513 CachingWrapperFilter attempts to cache null docIdSets

engine/src/main/java/org/hibernate/search/filter/impl/AndDocIdSet.java

@@ -75,8 +75,13 @@ private synchronized DocIdSet buildBitSet() throws IOException {
 		int size = andedDocIdSets.size();
 		DocIdSetIterator[] iterators = new DocIdSetIterator[size];
 		for ( int i = 0; i < size; i++ ) {
+			DocIdSet docIdSet = andedDocIdSets.get( i );
+			if ( docIdSet == null ) {
+				// Since Lucene 4 even the docIdSet could be returned at null to signify an empty match
+				return EMPTY_DOCIDSET;
+			}
 			// build all iterators
-			DocIdSetIterator docIdSetIterator = andedDocIdSets.get( i ).iterator();
+			DocIdSetIterator docIdSetIterator = docIdSet.iterator();
 			if ( docIdSetIterator == null ) {
 				// the Lucene API permits to return null on any iterator for empty matches
 				return EMPTY_DOCIDSET;

engine/src/main/java/org/hibernate/search/filter/impl/CachingWrapperFilter.java

@@ -40,8 +40,9 @@
  * the filter <code>BitSet</code>.
  *
  * @author Hardy Ferentschik
+ * @author Sanne Grinovero
  * @see org.apache.lucene.search.CachingWrapperFilter
- * @see <a href="http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-174">HSEARCH-174</a>
+ * @see <a href="https://hibernate.atlassian.net/browse/HSEARCH-174">HSEARCH-174</a>
  */
 @SuppressWarnings("serial")
 public class CachingWrapperFilter extends Filter {
@@ -50,6 +51,13 @@ public class CachingWrapperFilter extends Filter {
 
 	public static final int DEFAULT_SIZE = 5;
 
+	/**
+	 * Any Filter could return null as a value representing an empty match set,
+	 * we need to use NULL_OBJECT as a marker token to be able to cache this
+	 * return value.
+	 */
+	private static final Object NULL_OBJECT = new Object();
+
 	/**
 	 * The cache using soft references in order to store the filter bit sets.
 	 */
@@ -86,18 +94,34 @@ public CachingWrapperFilter(Filter filter, int size) {
 	@Override
 	public DocIdSet getDocIdSet(AtomicReaderContext context, Bits acceptDocs) throws IOException {
 		final AtomicReader reader = context.reader();
-		DocIdSet cached = (DocIdSet) cache.get( reader );
+		Object cached = cache.get( reader );
 		if ( cached != null ) {
-			return cached;
+			if ( cached == NULL_OBJECT ) {
+				return null;
+			}
+			else {
+				return (DocIdSet) cached;
+			}
 		}
 		synchronized ( cache ) {
-			cached = (DocIdSet) cache.get( reader );
+			cached = cache.get( reader );
 			if ( cached != null ) {
-				return cached;
+				if ( cached == NULL_OBJECT ) {
+					return null;
+				}
+				else {
+					return (DocIdSet) cached;
+				}
 			}
 			final DocIdSet docIdSet = filter.getDocIdSet( context, acceptDocs );
-			cache.put( reader, docIdSet );
-			return docIdSet;
+			if ( docIdSet == null ) {
+				cache.put( reader, NULL_OBJECT );
+				return null;
+			}
+			else {
+				cache.put( reader, docIdSet );
+				return docIdSet;
+			}
 		}
 	}
 

orm/src/test/java/org/hibernate/search/test/filter/Driver.java

@@ -63,7 +63,10 @@
 				cache = FilterCacheModeType.INSTANCE_ONLY),
 		@FullTextFilterDef(name = "empty",
 				impl = NullReturningEmptyFilter.class,
-				cache = FilterCacheModeType.INSTANCE_ONLY)
+				cache = FilterCacheModeType.INSTANCE_ONLY),
+		@FullTextFilterDef(name = "cached_empty",
+				impl = NullReturningEmptyFilter.class,
+				cache = FilterCacheModeType.INSTANCE_AND_DOCIDSETRESULTS)
 })
 public class Driver {
 	@Id

orm/src/test/java/org/hibernate/search/test/filter/FilterTest.java

@@ -38,6 +38,7 @@
 import org.hibernate.search.Search;
 import org.hibernate.search.SearchException;
 import org.hibernate.search.test.SearchTestCase;
+import org.hibernate.search.test.util.TestForIssue;
 
 /**
  * @author Emmanuel Bernard
@@ -127,6 +128,20 @@ public void testStraightFilters() {
 		assertEquals( "Should not filter anymore", 3, ftQuery.getResultSize() );
 	}
 
+	@TestForIssue(jiraKey = "HSEARCH-1513")
+	public void testCachedEmptyFilters() {
+		FullTextQuery ftQuery = fullTextSession.createFullTextQuery( query, Driver.class );
+		ftQuery.enableFullTextFilter( "bestDriver" );
+		Filter dateFilter = TermRangeFilter.newStringRange( "delivery", "2001", "2005", true, true );
+		ftQuery.setFilter( dateFilter );
+		assertEquals( "Should select only liz", 1, ftQuery.getResultSize() );
+
+		ftQuery = fullTextSession.createFullTextQuery( query, Driver.class );
+		ftQuery.enableFullTextFilter( "bestDriver" );
+		ftQuery.enableFullTextFilter( "cached_empty" );
+		assertEquals( "two filters, one is empty, should not match anything", 0, ftQuery.getResultSize() );
+	}
+
 	public void testMultipleFiltersOfSameTypeWithDifferentParameters() {
 		FullTextQuery ftQuery = fullTextSession.createFullTextQuery( query, Driver.class );
 		ftQuery.enableFullTextFilter( "fieldConstraintFilter-1" )

orm/src/test/java/org/hibernate/search/test/filter/NullReturningEmptyFilter.java

@@ -24,34 +24,20 @@
 
 import org.apache.lucene.index.AtomicReaderContext;
 import org.apache.lucene.search.DocIdSet;
-import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.util.Bits;
 
 /**
  * Apparently it's legal for Lucene filters to return null
- * on {@link DocIdSet#iterator()} : make sure we can deal with it as well.
+ * on {@link Filter#getDocIdSet} : make sure we can deal with it as well.
  *
  * @author Sanne Grinovero <sanne@hibernate.org> (C) 2011 Red Hat Inc.
  */
 public class NullReturningEmptyFilter extends Filter implements Serializable {
 
-	public static final DocIdSet EMPTY_DOCIDSET = new DocIdSet() {
-
-		@Override
-		public DocIdSetIterator iterator() {
-			return null;
-		}
-
-		@Override
-		public boolean isCacheable() {
-			return true;
-		}
-	};
-
 	@Override
 	public DocIdSet getDocIdSet(AtomicReaderContext context, Bits acceptDocs) throws IOException {
-		return EMPTY_DOCIDSET;
+		return null;
 	}
 
 }