GH-5653 experimenting with query optimisation for union and optional implementated based on paper

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/ArrayBindingSet.java

@@ -8,10 +8,12 @@
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *******************************************************************************/
+// Some portions generated by Codex
 package org.eclipse.rdf4j.query.algebra.evaluation;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.BitSet;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
@@ -43,13 +45,22 @@ public class ArrayBindingSet extends AbstractBindingSet implements MutableBindin
 
 	private static final long serialVersionUID = -1L;
 
+	@InternalUseOnly
+	public interface BindingNamesCache {
+		Set<String> getBindingNames(long presentMask);
+
+		Set<String> getBindingNames(BitSet presentMask);
+	}
+
 	private static final Logger logger = LoggerFactory.getLogger(ArrayBindingSet.class);
 	private static final Value NULL_VALUE = Values
 			.iri("urn:null:d57c56f3-41a9-468e-8dce-5706ebdef84c_e88d9e52-27cb-4056-a889-1ea353fa6f0c");
 
+	private final BindingNamesCache bindingNamesCache;
 	private final String[] bindingNames;
 
-	// Creating a LinkedHashSet is expensive, so we should cache the binding names set
+	// Creating a LinkedHashSet is expensive, so we should cache the binding names set (and ideally share it across
+	// ArrayBindingSet instances created by the same QueryEvaluationContext).
 	private Set<String> bindingNamesSetCache;
 	private boolean empty;
 
@@ -64,14 +75,27 @@ public class ArrayBindingSet extends AbstractBindingSet implements MutableBindin
 	 * @param names The binding names.
 	 */
 	public ArrayBindingSet(String... names) {
+		this((BindingNamesCache) null, names);
+	}
+
+	@InternalUseOnly
+	public ArrayBindingSet(BindingNamesCache bindingNamesCache, String... names) {
+		this.bindingNamesCache = bindingNamesCache;
 		this.bindingNames = names;
 		this.values = new Value[names.length];
 		this.empty = true;
 	}
 
 	public ArrayBindingSet(BindingSet toCopy, Set<String> names, String[] namesArray) {
+		this(null, toCopy, names, namesArray);
+	}
+
+	@InternalUseOnly
+	public ArrayBindingSet(BindingNamesCache bindingNamesCache, BindingSet toCopy, Set<String> names,
+			String[] namesArray) {
 		assert !(toCopy instanceof ArrayBindingSet);
 
+		this.bindingNamesCache = bindingNamesCache;
 		this.bindingNames = namesArray;
 		this.values = new Value[this.bindingNames.length];
 		for (int i = 0; i < this.bindingNames.length; i++) {
@@ -92,6 +116,12 @@ public ArrayBindingSet(BindingSet toCopy, Set<String> names, String[] namesArray
 	}
 
 	public ArrayBindingSet(ArrayBindingSet toCopy, String... names) {
+		this(null, toCopy, names);
+	}
+
+	@InternalUseOnly
+	public ArrayBindingSet(BindingNamesCache bindingNamesCache, ArrayBindingSet toCopy, String... names) {
+		this.bindingNamesCache = bindingNamesCache;
 		this.bindingNames = names;
 
 		this.values = Arrays.copyOf(toCopy.values, toCopy.values.length);
@@ -191,32 +221,80 @@ public Set<String> getBindingNames() {
 			return Collections.emptySet();
 		}
 
-		if (bindingNamesSetCache == null) {
-			int size = size();
-			if (size == 0) {
-				this.bindingNamesSetCache = Collections.emptySet();
-			} else if (size == 1) {
-				for (int i = 0; i < this.bindingNames.length; i++) {
-					if (values[i] != null) {
-						this.bindingNamesSetCache = Collections.singleton(bindingNames[i]);
-						break;
-					}
-				}
-				assert this.bindingNamesSetCache != null;
+		if (bindingNamesSetCache != null) {
+			return bindingNamesSetCache;
+		}
+
+		Set<String> bindingNamesSetCache;
+		if (bindingNamesCache != null) {
+			if (bindingNames.length <= Long.SIZE) {
+				bindingNamesSetCache = bindingNamesCache.getBindingNames(toLongMask());
 			} else {
-				LinkedHashSet<String> bindingNamesSetCache = new LinkedHashSet<>(size * 2);
-				for (int i = 0; i < this.bindingNames.length; i++) {
-					if (values[i] != null) {
-						bindingNamesSetCache.add(bindingNames[i]);
-					}
-				}
-				this.bindingNamesSetCache = Collections.unmodifiableSet(bindingNamesSetCache);
+				bindingNamesSetCache = bindingNamesCache.getBindingNames(toBitSet());
 			}
+		} else if (bindingNames.length <= Long.SIZE) {
+			bindingNamesSetCache = toSetFromLongMask(toLongMask());
+		} else {
+			bindingNamesSetCache = toSetFromBitSet(toBitSet());
 		}
 
+		this.bindingNamesSetCache = bindingNamesSetCache;
 		return bindingNamesSetCache;
 	}
 
+	private long toLongMask() {
+		long mask = 0;
+		for (int i = 0; i < values.length; i++) {
+			if (values[i] != null) {
+				mask |= (1L << i);
+			}
+		}
+		return mask;
+	}
+
+	private BitSet toBitSet() {
+		BitSet bitSet = new BitSet(values.length);
+		for (int i = 0; i < values.length; i++) {
+			if (values[i] != null) {
+				bitSet.set(i);
+			}
+		}
+		return bitSet;
+	}
+
+	private Set<String> toSetFromLongMask(long mask) {
+		int size = Long.bitCount(mask);
+		if (size == 0) {
+			return Collections.emptySet();
+		}
+		if (size == 1) {
+			return Collections.singleton(bindingNames[Long.numberOfTrailingZeros(mask)]);
+		}
+
+		LinkedHashSet<String> set = new LinkedHashSet<>(size * 2);
+		for (long bits = mask; bits != 0; bits &= (bits - 1)) {
+			int index = Long.numberOfTrailingZeros(bits);
+			set.add(bindingNames[index]);
+		}
+		return Collections.unmodifiableSet(set);
+	}
+
+	private Set<String> toSetFromBitSet(BitSet bitSet) {
+		int size = bitSet.cardinality();
+		if (size == 0) {
+			return Collections.emptySet();
+		}
+		if (size == 1) {
+			return Collections.singleton(bindingNames[bitSet.nextSetBit(0)]);
+		}
+
+		LinkedHashSet<String> set = new LinkedHashSet<>(size * 2);
+		for (int index = bitSet.nextSetBit(0); index >= 0; index = bitSet.nextSetBit(index + 1)) {
+			set.add(bindingNames[index]);
+		}
+		return Collections.unmodifiableSet(set);
+	}
+
 	@Override
 	public Value getValue(String bindingName) {
 		if (isEmpty()) {

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/BulkTripleSource.java

@@ -0,0 +1,30 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Eclipse RDF4J contributors.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Distribution License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *******************************************************************************/
+// Some portions generated by Codex
+package org.eclipse.rdf4j.query.algebra.evaluation;
+
+import org.eclipse.rdf4j.common.iteration.CloseableIteration;
+import org.eclipse.rdf4j.common.order.StatementOrder;
+import org.eclipse.rdf4j.model.Resource;
+import org.eclipse.rdf4j.query.BindingSet;
+import org.eclipse.rdf4j.query.QueryEvaluationException;
+import org.eclipse.rdf4j.query.algebra.StatementPattern;
+
+/**
+ * Optional capability for evaluating a StatementPattern against multiple bindings at once.
+ */
+public interface BulkTripleSource extends TripleSource {
+
+	CloseableIteration<BindingSet> getStatementsBatch(StatementPattern statementPattern,
+			Iterable<BindingSet> bindings,
+			Resource[] contexts,
+			StatementOrder order) throws QueryEvaluationException;
+}