HHH-15342 Inappropriate variation of HQL left join to SQL inner join

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/ToOneAttributeMapping.java

@@ -1196,8 +1196,32 @@ public class ToOneAttributeMapping
 				|| fetchParent.getNavigablePath() instanceof TreatedNavigablePath
 				&& parentNavigablePath.equals( fetchParent.getNavigablePath().getRealParent() );
 
+		/*
+		 In case of @NotFound we are going to add fetch for the `fetchablePath` only if there is not already a `TableGroupJoin`.
 
-		if ( (hasNotFoundAction()
+		 e.g. given :
+		 	public static class EntityA {
+				...
+
+			@ManyToOne(fetch = FetchType.LAZY)
+			@NotFound(action = NotFoundAction.IGNORE)
+			private EntityB entityB;
+		 	}
+
+			@Entity(name = "EntityB")
+			public static class EntityB {
+				...
+
+				private String name;
+			}
+
+		 and the HQL query :
+
+		 `Select a From EntityA a Left Join a.entityB b Where ( b.name IS NOT NULL )`
+
+		 having the left join we don't want to add an extra implicit join that will be translated into an SQL inner join (see HHH-15342)
+		*/
+		if ( ( ( hasNotFoundAction() && doesNotExistATableGroupJoin( parentTableGroup, fetchablePath ) )
 				|| ( fetchTiming == FetchTiming.IMMEDIATE && selected ) ) ) {
 			final TableGroup tableGroup = determineTableGroup(
 					fetchablePath,
@@ -1308,6 +1332,15 @@ public class ToOneAttributeMapping
 		);
 	}
 
+	private boolean doesNotExistATableGroupJoin(TableGroup parentTableGroup, NavigablePath fetchablePath) {
+		for ( TableGroupJoin tableGroupJoin : parentTableGroup.getTableGroupJoins() ) {
+			if ( tableGroupJoin.getNavigablePath().pathsMatch( fetchablePath ) ) {
+				return false;
+			}
+		}
+		return true;
+	}
+
 	private TableGroup determineTableGroup(NavigablePath fetchablePath, FetchParent fetchParent, TableGroup parentTableGroup, String resultVariable, FromClauseAccess fromClauseAccess, DomainResultCreationState creationState) {
 		final TableGroup tableGroup;
 		if ( fetchParent instanceof EntityResultJoinedSubclassImpl
@@ -1321,6 +1354,10 @@ public class ToOneAttributeMapping
 					false,
 					creationState.getSqlAstCreationState()
 			);
+			if ( hasNotFoundAction() ) {
+				tableGroupJoin.setImplicit();
+			}
+
 			parentTableGroup.addTableGroupJoin( tableGroupJoin );
 			tableGroup = tableGroupJoin.getJoinedGroup();
 			fromClauseAccess.registerTableGroup( fetchablePath, tableGroup );
@@ -1338,6 +1375,9 @@ public class ToOneAttributeMapping
 								false,
 								creationState.getSqlAstCreationState()
 						);
+						if ( hasNotFoundAction() ) {
+							tableGroupJoin.setImplicit();
+						}
 						parentTableGroup.addTableGroupJoin( tableGroupJoin );
 						return tableGroupJoin.getJoinedGroup();
 					}

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/BaseSqmToSqlAstConverter.java

@@ -3209,7 +3209,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 				final NavigablePath parentParentPath = parentPath.getParentPath().getNavigablePath();
 				final TableGroup parentParentTableGroup = fromClauseIndex.findTableGroup( parentParentPath );
 				parentParentTableGroup.visitTableGroupJoins( (join) -> {
-					if ( join.getNavigablePath().equals( parentPath.getNavigablePath() ) ) {
+					if ( join.getNavigablePath().equals( parentPath.getNavigablePath() ) && join.isImplicit() ) {
 						join.setJoinType( SqlAstJoinType.INNER );
 					}
 				} );
@@ -3312,6 +3312,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 							false,
 							this
 					);
+					tableGroupJoin.setImplicit();
 					// Implicit joins in the ON clause of attribute joins need to be added as nested table group joins
 					// We don't have to do that for entity joins etc. as these do not have an inherent dependency on the lhs.
 					// We can just add the implicit join before the currently processing join

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableGroupJoin.java

@@ -27,6 +27,8 @@ public class TableGroupJoin implements TableJoin, DomainResultProducer {
 	private SqlAstJoinType joinType;
 	private Predicate predicate;
 
+	private boolean implicit;
+
 	public TableGroupJoin(
 			NavigablePath navigablePath,
 			SqlAstJoinType joinType,
@@ -91,6 +93,14 @@ public class TableGroupJoin implements TableJoin, DomainResultProducer {
 		return navigablePath;
 	}
 
+	public void setImplicit(){
+		this.implicit = true;
+	}
+
+	public boolean isImplicit(){
+		return implicit;
+	}
+
 	@Override
 	public DomainResult createDomainResult(
 			String resultVariable,

hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/internal/EntityFetchSelectImpl.java

@@ -36,8 +36,6 @@ public class EntityFetchSelectImpl extends AbstractNonJoinedEntityFetch {
 			@SuppressWarnings("unused") DomainResultCreationState creationState) {
 		super( navigablePath, fetchedAttribute, fetchParent );
 
-		assert fetchedAttribute.getNotFoundAction() == null;
-
 		this.keyResult = keyResult;
 		this.selectByUniqueKey = selectByUniqueKey;
 	}