HHH-8901 Some very minor string handling optimisations

hibernate-core/src/main/java/org/hibernate/criterion/InExpression.java

@@ -10,6 +10,7 @@ import java.util.ArrayList;
 
 import org.hibernate.Criteria;
 import org.hibernate.EntityMode;
+import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.spi.TypedValue;
 import org.hibernate.internal.util.StringHelper;
 import org.hibernate.type.CompositeType;
@@ -41,22 +42,20 @@ public class InExpression implements Criterion {
 	@Override
 	public String toSqlString( Criteria criteria, CriteriaQuery criteriaQuery ) {
 		final String[] columns = criteriaQuery.findColumns( propertyName, criteria );
-		if ( criteriaQuery.getFactory().getDialect().supportsRowValueConstructorSyntaxInInList() || columns.length <= 1 ) {
+		Dialect dialect = criteriaQuery.getFactory().getDialect();
+		if ( dialect.supportsRowValueConstructorSyntaxInInList() || columns.length <= 1 ) {
 			String singleValueParam = StringHelper.repeat( "?, ", columns.length - 1 ) + "?";
 			if ( columns.length > 1 ) {
 				singleValueParam = '(' + singleValueParam + ')';
 			}
-			String params = values.length > 0
+			final String params = values.length > 0
 					? StringHelper.repeat( singleValueParam + ", ", values.length - 1 ) + singleValueParam
-					: "";
+					// Deal with HHH-8901 : not all databases like to have an empty list.
+					: dialect.supportsEmptyInList() ? "" : "null";
 			String cols = String.join( ", ", columns );
 			if ( columns.length > 1 ) {
 				cols = '(' + cols + ')';
 			}
-			// HHH-8901
-			if ( ! criteriaQuery.getFactory().getDialect().supportsEmptyInList() && params.isEmpty() ) {
-				params = "null";
-			}
 			return cols + " in (" + params + ')';
 		}
 		else {

hibernate-core/src/main/java/org/hibernate/query/criteria/internal/predicate/InPredicate.java

@@ -181,24 +181,32 @@ public class InPredicate<T>
 
 		// subquery expressions are already wrapped in parenthesis, so we only need to
 		// render the parenthesis here if the values represent an explicit value list
-		boolean isInSubqueryPredicate = getValues().size() == 1
-				&& Subquery.class.isInstance( getValues().get( 0 ) );
+		List<Expression<? extends T>> values = getValues();
+		boolean isInSubqueryPredicate = values.size() == 1
+				&& Subquery.class.isInstance( values.get( 0 ) );
 		if ( isInSubqueryPredicate ) {
-			buffer.append( ( (Renderable) getValues().get(0) ).render( renderingContext ) );
+			buffer.append( ( (Renderable) values.get( 0 ) ).render( renderingContext ) );
 		}
 		else {
-			buffer.append( '(' );
-			String sep = "";
-			for ( Expression value : getValues() ) {
-				buffer.append( sep )
-						.append( ( (Renderable) value ).render( renderingContext ) );
-				sep = ", ";
+			if ( values.isEmpty() ) {
+				if ( renderingContext.getDialect().supportsEmptyInList() ) {
+					buffer.append( "()" );
+				}
+				else {
+					buffer.append( "(null)" );
+				}
 			}
-			// HHH-8901
-			if ( ! renderingContext.getDialect().supportsEmptyInList() && getValues().isEmpty() ) {
-				buffer.append( "null" );
+			else {
+				buffer.append( '(' );
+				String sep = "";
+				for ( Expression value : values) {
+					buffer.append( sep )
+							.append( ( (Renderable) value )
+									.render( renderingContext ) );
+					sep = ", ";
+				}
+				buffer.append( ')' );
 			}
-			buffer.append( ')' );
 		}
 		return buffer.toString();
 	}

hibernate-core/src/main/java/org/hibernate/query/internal/QueryParameterBindingsImpl.java

@@ -637,16 +637,18 @@ public class QueryParameterBindingsImpl implements QueryParameterBindings {
 				parameterBindingMap.put( syntheticParam, syntheticBinding );
 			}
 
+			String expansionListAsString = expansionList.toString();
+
 			// HHH-8901
-			if ( ! dialect.supportsEmptyInList() && expansionList.length() == 0 ) {
-				expansionList.append( "null" );
+			if ( ! dialect.supportsEmptyInList() && expansionListAsString.isEmpty() ) {
+				expansionListAsString = "null";
 			}
 
 			queryString = StringHelper.replace(
 					beforePlaceholder,
 					afterPlaceholder,
 					sourceToken,
-					expansionList.toString(),
+					expansionListAsString,
 					true,
 					true
 			);