HHH-6723 : Remove extra join from eager @OneToOne

hibernate-core/src/main/java/org/hibernate/loader/AbstractEntityJoinWalker.java

@@ -25,6 +25,7 @@
 package org.hibernate.loader;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Iterator;
 
@@ -186,6 +187,21 @@ public abstract class AbstractEntityJoinWalker extends JoinWalker {
 
 	public abstract String getComment();
 
+	@Override
+    protected boolean isDuplicateAssociation(
+		final String foreignKeyTable,
+		final String[] foreignKeyColumns
+	) {
+		//disable a join back to this same association
+		final boolean isSameJoin =
+				persister.getTableName().equals( foreignKeyTable ) &&
+						Arrays.equals( foreignKeyColumns, persister.getKeyColumnNames() );
+		return isSameJoin ||
+			super.isDuplicateAssociation(foreignKeyTable, foreignKeyColumns);
+	}
+
+
+
 	protected final Loadable getPersister() {
 		return persister;
 	}

hibernate-testsuite/src/test/java/org/hibernate/test/annotations/onetoone/OneToOneTest.java

@@ -299,19 +299,11 @@ public class OneToOneTest extends TestCase {
 	}
 
 	/**
-	 * HHH-5109 @OneToOne - too many joins
-	 * I backed out of the fix for HHH-5109 because it caused HHH-4982.
-	 * It needs to be fixed again by HHH-6723.
-	 *
 	 * This test uses an interceptor to verify that correct number of joins
 	 * are generated.
 	 */
 	public void testPkOneToOneSelectStatementDoesNotGenerateExtraJoin() {
-
-	 	//"FailureExpected" doesn't work here, so until it is fixed (again) by HHH-6723,
-		// we expect an extra join, new JoinCounter(2) is used to get the test to pass.
-		// Session s = openSession(new JoinCounter(1));
-		Session s = openSession(new JoinCounter(2));
+		Session s = openSession(new JoinCounter(1));
 		Transaction tx = s.beginTransaction();
 		Owner owner = new Owner();
 		OwnerAddress address = new OwnerAddress();