HHH-15719 Hint UniqueSematics.NONE for entity queries without collection join fetches

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

@@ -18,6 +18,10 @@ import org.hibernate.engine.spi.EntityKey;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.engine.spi.SubselectFetch;
+import org.hibernate.graph.spi.AppliedGraph;
+import org.hibernate.graph.spi.AttributeNodeImplementor;
+import org.hibernate.graph.spi.GraphImplementor;
+import org.hibernate.graph.spi.SubGraphImplementor;
 import org.hibernate.internal.EmptyScrollableResults;
 import org.hibernate.internal.util.collections.ArrayHelper;
 import org.hibernate.metamodel.mapping.MappingModelExpressible;
@@ -86,6 +90,13 @@ public class ConcreteSqmSelectQueryPlan<R> implements SelectQueryPlan<R> {
 
 		this.rowTransformer = determineRowTransformer( sqm, resultType, tupleMetadata, queryOptions );
 
+		final ListResultsConsumer.UniqueSemantic uniqueSemantic;
+		if ( sqm.producesUniqueResults() && !containsCollectionFetches( queryOptions ) ) {
+			uniqueSemantic = ListResultsConsumer.UniqueSemantic.NONE;
+		}
+		else {
+			uniqueSemantic = ListResultsConsumer.UniqueSemantic.ALLOW;
+		}
 		this.listInterpreter = (unused, executionContext, sqmInterpretation, jdbcParameterBindings) -> {
 			final SharedSessionContractImplementor session = executionContext.getSession();
 			final JdbcSelect jdbcSelect = sqmInterpretation.getJdbcSelect();
@@ -122,7 +133,7 @@ public class ConcreteSqmSelectQueryPlan<R> implements SelectQueryPlan<R> {
 							}
 						},
 						rowTransformer,
-						ListResultsConsumer.UniqueSemantic.ALLOW
+						uniqueSemantic
 				);
 			}
 			finally {
@@ -168,6 +179,25 @@ public class ConcreteSqmSelectQueryPlan<R> implements SelectQueryPlan<R> {
 		//		`#performList` and `#performScroll`.
 	}
 
+	private static boolean containsCollectionFetches(QueryOptions queryOptions) {
+		final AppliedGraph appliedGraph = queryOptions.getAppliedGraph();
+		return appliedGraph != null && appliedGraph.getGraph() != null && containsCollectionFetches( appliedGraph.getGraph() );
+	}
+
+	private static boolean containsCollectionFetches(GraphImplementor<?> graph) {
+		for ( AttributeNodeImplementor<?> attributeNodeImplementor : graph.getAttributeNodeImplementors() ) {
+			if ( attributeNodeImplementor.getAttributeDescriptor().isCollection() ) {
+				return true;
+			}
+			for ( SubGraphImplementor<?> subGraph : attributeNodeImplementor.getSubGraphMap().values() ) {
+				if ( containsCollectionFetches( subGraph ) ) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
 	@SuppressWarnings("unchecked")
 	private RowTransformer<R> determineRowTransformer(
 			SqmSelectStatement<?> sqm,

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmQuerySpec.java

@@ -146,6 +146,41 @@ public class SqmQuerySpec<T> extends SqmQueryPart<T>
 		this.fromClause = fromClause;
 	}
 
+	public boolean producesUniqueResults() {
+		if ( fromClause.getRoots().size() != 1 ) {
+			return false;
+		}
+		final SqmRoot<?> sqmRoot = fromClause.getRoots().get( 0 );
+		if ( selectClause != null ) {
+			final List<SqmSelection<?>> selections = selectClause.getSelections();
+			if ( selections.size() != 1 || selections.get( 0 ).getSelectableNode() != sqmRoot ) {
+				// If we select anything but the query root, let's be pessimistic about unique results
+				return false;
+			}
+		}
+		final List<SqmFrom<?, ?>> fromNodes = new ArrayList<>( sqmRoot.getSqmJoins().size() + 1 );
+		fromNodes.add( sqmRoot );
+		while ( !fromNodes.isEmpty() ) {
+			final SqmFrom<?, ?> fromNode = fromNodes.remove( fromNodes.size() - 1 );
+			for ( SqmJoin<?, ?> sqmJoin : fromNode.getSqmJoins() ) {
+				if ( sqmJoin instanceof SqmAttributeJoin<?, ?> ) {
+					final SqmAttributeJoin<?, ?> join = (SqmAttributeJoin<?, ?>) sqmJoin;
+					if ( join.getAttribute().isCollection() ) {
+						// Collections joins always alter cardinality
+						return false;
+					}
+				}
+				else {
+					// For now, consider all non-attribute joins as cardinality altering
+					return false;
+				}
+				fromNodes.add( sqmJoin );
+			}
+			fromNodes.addAll( fromNode.getSqmTreats() );
+		}
+		return true;
+	}
+
 	public boolean containsCollectionFetches() {
 		final List<SqmFrom<?, ?>> fromNodes = new ArrayList<>( fromClause.getRoots() );
 		while ( !fromNodes.isEmpty() ) {
@@ -159,6 +194,7 @@ public class SqmQuerySpec<T> extends SqmQueryPart<T>
 				}
 				fromNodes.add( sqmJoin );
 			}
+			fromNodes.addAll( fromNode.getSqmTreats() );
 		}
 		return false;
 	}

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmSelectStatement.java

@@ -153,6 +153,20 @@ public class SqmSelectStatement<T> extends AbstractSqmSelectQuery<T> implements
 		}
 	}
 
+	public boolean producesUniqueResults() {
+		return producesUniqueResults( getQueryPart() );
+	}
+
+	private boolean producesUniqueResults(SqmQueryPart<?> queryPart) {
+		if ( queryPart instanceof SqmQuerySpec<?> ) {
+			return ( (SqmQuerySpec<?>) queryPart ).producesUniqueResults();
+		}
+		else {
+			// For query groups we have to assume that duplicates are possible
+			return true;
+		}
+	}
+
 	public boolean containsCollectionFetches() {
 		return containsCollectionFetches( getQueryPart() );
 	}