GH-5447 LMDB Store query performance improvements

core/common/iterator/src/main/java/org/eclipse/rdf4j/common/iteration/CloseableIteration.java

@@ -14,6 +14,8 @@
 import java.util.Iterator;
 import java.util.stream.Stream;
 
+import org.eclipse.rdf4j.model.Statement;
+
 /**
  * An {@link CloseableIteration} that can be closed to free resources that it is holding. CloseableIterations
  * automatically free their resources when exhausted. If not read until exhaustion or if you want to make sure the
@@ -33,6 +35,8 @@
  */
 public interface CloseableIteration<E> extends Iterator<E>, AutoCloseable {
 
+	EmptyIteration<Statement> EMPTY_STATEMENT_ITERATION = new EmptyIteration<>();
+
 	/**
 	 * Convert the results to a Java 8 Stream.
 	 *

core/common/iterator/src/main/java/org/eclipse/rdf4j/common/iteration/DualUnionIteration.java

@@ -50,7 +50,11 @@ public DualUnionIteration(Comparator<E> cmp,
 	public static <E> CloseableIteration<? extends E> getWildcardInstance(
 			CloseableIteration<? extends E> leftIteration, CloseableIteration<? extends E> rightIteration) {
 
-		if (rightIteration instanceof EmptyIteration) {
+		if (leftIteration == EMPTY_STATEMENT_ITERATION) {
+			return rightIteration;
+		} else if (rightIteration == EMPTY_STATEMENT_ITERATION) {
+			return leftIteration;
+		} else if (rightIteration instanceof EmptyIteration) {
 			return leftIteration;
 		} else if (leftIteration instanceof EmptyIteration) {
 			return rightIteration;
@@ -63,7 +67,11 @@ public static <E> CloseableIteration<? extends E> getWildcardInstance(
 	public static <E> CloseableIteration<? extends E> getWildcardInstance(Comparator<E> cmp,
 			CloseableIteration<? extends E> leftIteration, CloseableIteration<? extends E> rightIteration) {
 
-		if (rightIteration instanceof EmptyIteration) {
+		if (leftIteration == EMPTY_STATEMENT_ITERATION) {
+			return rightIteration;
+		} else if (rightIteration == EMPTY_STATEMENT_ITERATION) {
+			return leftIteration;
+		} else if (rightIteration instanceof EmptyIteration) {
 			return leftIteration;
 		} else if (leftIteration instanceof EmptyIteration) {
 			return rightIteration;
@@ -75,7 +83,11 @@ public static <E> CloseableIteration<? extends E> getWildcardInstance(Comparator
 	public static <E> CloseableIteration<E> getInstance(CloseableIteration<E> leftIteration,
 			CloseableIteration<E> rightIteration) {
 
-		if (rightIteration instanceof EmptyIteration) {
+		if (leftIteration == EMPTY_STATEMENT_ITERATION) {
+			return rightIteration;
+		} else if (rightIteration == EMPTY_STATEMENT_ITERATION) {
+			return leftIteration;
+		} else if (rightIteration instanceof EmptyIteration) {
 			return leftIteration;
 		} else if (leftIteration instanceof EmptyIteration) {
 			return rightIteration;

core/query/src/main/java/org/eclipse/rdf4j/query/AbstractBindingSet.java

@@ -26,6 +26,9 @@ public abstract class AbstractBindingSet implements BindingSet {
 
 	@Override
 	public boolean equals(Object other) {
+		if (other == null) {
+			return false;
+		}
 		if (this == other) {
 			return true;
 		}

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

@@ -403,6 +403,23 @@ public void addAll(ArrayBindingSet other) {
 
 	}
 
+//	@Override
+//	public boolean equals(Object other){
+//		if(other == null) return false;
+//		if(other == this) return true;
+//
+//		if(other.getClass() != ArrayBindingSet.class){
+//			return super.equals(other);
+//		}
+//
+//		ArrayBindingSet that = (ArrayBindingSet) other;
+//
+//		// TODO make a faster equals for ArrayBindingSet
+//		return super.equals(that);
+//
+//
+//	}
+
 	private class ArrayBindingSetIterator implements Iterator<Binding> {
 
 		private int index = 0;

core/sail/base/src/main/java/org/eclipse/rdf4j/sail/base/SailDatasetImpl.java

@@ -46,7 +46,6 @@ class SailDatasetImpl implements SailDataset {
 
 	private static final EmptyIteration<Triple> TRIPLE_EMPTY_ITERATION = new EmptyIteration<>();
 	private static final EmptyIteration<Namespace> NAMESPACES_EMPTY_ITERATION = new EmptyIteration<>();
-	private static final EmptyIteration<Statement> STATEMENT_EMPTY_ITERATION = new EmptyIteration<>();
 
 	/**
 	 * {@link SailDataset} of the backing {@link SailSource}.
@@ -286,7 +285,7 @@ public CloseableIteration<? extends Statement> getStatements(Resource subj, IRI
 		} else if (iter != null) {
 			return iter;
 		} else {
-			return STATEMENT_EMPTY_ITERATION;
+			return CloseableIteration.EMPTY_STATEMENT_ITERATION;
 		}
 	}