HHH-16397 Allow fk optimization for correlated paths in subqueries

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

@@ -2058,9 +2058,9 @@ else if ( isNullable || hasNotFoundAction() ) {
 		}
 
 		final TableGroupProducer tableGroupProducer;
-		if ( realParentTableGroup instanceof CorrelatedTableGroup ) {
-			// If the parent is a correlated table group, we can't refer to columns of the table in the outer query,
-			// because the context in which a column is used could be an aggregate function.
+		if ( requestedJoinType != null && realParentTableGroup instanceof CorrelatedTableGroup ) {
+			// If the parent is a correlated table group, and we're explicitly joining, we can't refer to columns of the
+			// table in the outer query, because the context in which a column is used could be an aggregate function.
 			// Using a parent column in such a case would lead to an error if the parent query lacks a proper group by
 			tableGroupProducer = entityMappingType;
 		}
@@ -2105,7 +2105,7 @@ else if ( isNullable || hasNotFoundAction() ) {
 			);
 		}
 
-		if ( realParentTableGroup instanceof CorrelatedTableGroup ) {
+		if ( requestedJoinType != null && realParentTableGroup instanceof CorrelatedTableGroup ) {
 			// Force initialization of the underlying table group join to retain cardinality
 			lazyTableGroup.getPrimaryTableReference();
 		}

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

@@ -208,13 +208,8 @@ private static <T> EntityValuedPathInterpretation<T> from(
 							.findTableGroup( tableGroup.getNavigablePath().getParent() );
 				}
 				else {
-					if ( isCorrelated( tableGroup, sqlAstCreationState )
-							|| !tableGroup.getNavigablePath().isParentOrEqual( navigablePath ) ) {
-						// Access to the parent table group is forbidden for correlated table groups. For more details,
-						// see: `ToOneAttributeMapping.createRootTableGroupJoin`
-						// Due to that, we forcefully use the model part to which this association points to i.e. the target
-
-						// Also force the use of the FK target key if the navigable path for this entity valued path is
+					if ( !tableGroup.getNavigablePath().isParentOrEqual( navigablePath ) ) {
+						// Force the use of the FK target key if the navigable path for this entity valued path is
 						// not equal to or a child of the table group navigable path.
 						// This can happen when using an implicit join path e.g. `where root.association.id is null`,
 						// yet also an explicit join was made which is compatible e.g. `join fetch root.association`.
@@ -261,21 +256,6 @@ else if ( mapping instanceof AnonymousTupleEntityValuedModelPart ) {
 		);
 	}
 
-	private static boolean isCorrelated(TableGroup tableGroup, SqmToSqlAstConverter sqlAstCreationState) {
-		final SqlAstProcessingState processingState = sqlAstCreationState.getCurrentProcessingState();
-		if ( !( processingState instanceof SqlAstQueryPartProcessingState )
-				|| ( (SqlAstQueryPartProcessingState) processingState ).getInflightQueryPart().isRoot() ) {
-			return false;
-		}
-		final FromClauseAccess fromClauseAccess = sqlAstCreationState.getFromClauseAccess();
-
-		TableGroup realParentTableGroup = fromClauseAccess.findTableGroup( tableGroup.getNavigablePath().getParent() );
-		while ( realParentTableGroup.getModelPart() instanceof EmbeddableValuedModelPart ) {
-			realParentTableGroup = fromClauseAccess.findTableGroup( realParentTableGroup.getNavigablePath().getParent() );
-		}
-		return realParentTableGroup instanceof CorrelatedTableGroup;
-	}
-
 	private static boolean hasNotFound(EntityValuedModelPart mapping) {
 		return mapping instanceof ToOneAttributeMapping && ( (ToOneAttributeMapping) mapping ).hasNotFoundAction();
 	}

hibernate-core/src/main/java/org/hibernate/sql/ast/spi/AbstractSqlAstTranslator.java

@@ -5128,7 +5128,7 @@ private String renderFromClauseRoot(TableGroup root, String separator) {
 				separator = renderFromClauseRoot( tableGroupJoin.getJoinedGroup(), separator );
 			}
 		}
-		else {
+		else if ( root.isInitialized() ) {
 			appendSql( separator );
 			renderRootTableGroup( root, null );
 			separator = COMA_SEPARATOR;