HHH-18783 cast(x as Character) on MySQL and Maria

hibernate-core/src/main/java/org/hibernate/dialect/MariaDBSqlAstTranslator.java

@@ -401,5 +401,4 @@ protected void renderStringContainsExactlyPredicate(Expression haystack, Express
 		needle.accept( this );
 		appendSql( ",'~','~~'),'?','~?'),'%','~%'),'%') escape '~'" );
 	}
-
 }

hibernate-core/src/main/java/org/hibernate/dialect/MySQLDialect.java

@@ -129,6 +129,7 @@ public class MySQLDialect extends Dialect {
 	private static final DatabaseVersion MINIMUM_VERSION = DatabaseVersion.make( 8 );
 
 	private final MySQLStorageEngine storageEngine = createStorageEngine();
+
 	private final SizeStrategy sizeStrategy = new SizeStrategyImpl() {
 		@Override
 		public Size resolveSize(

hibernate-core/src/main/java/org/hibernate/dialect/MySQLSqlAstTranslator.java

@@ -4,10 +4,6 @@
  */
 package org.hibernate.dialect;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Locale;
-
 import org.hibernate.engine.jdbc.Size;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.internal.util.collections.Stack;
@@ -41,6 +37,10 @@
 import org.hibernate.sql.exec.spi.JdbcOperation;
 import org.hibernate.sql.exec.spi.JdbcOperationQueryInsert;
 
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+
 /**
  * A SQL AST translator for MySQL.
  *
@@ -57,6 +57,10 @@ public static String getSqlType(CastTarget castTarget, SessionFactoryImplementor
 		return getSqlType( castTarget, sqlType, factory.getJdbcServices().getDialect() );
 	}
 
+	//TODO: this is really, really bad since it circumvents the whole machinery we have in DdlType
+	//      and in the Dialect for doing this in a unified way! These mappings should be held in
+	//      the DdlTypes themselves and should be set up in registerColumnTypes(). Doing it here
+	//      means we have problems distinguishing, say, the 'as Character' special case
 	private static String getSqlType(CastTarget castTarget, String sqlType, Dialect dialect) {
 		if ( sqlType != null ) {
 			int parenthesesIndex = sqlType.indexOf( '(' );
@@ -72,23 +76,30 @@ private static String getSqlType(CastTarget castTarget, String sqlType, Dialect
 				case "float":
 				case "real":
 				case "double precision":
-					final int precision = castTarget.getPrecision() == null ?
-							dialect.getDefaultDecimalPrecision() :
-							castTarget.getPrecision();
+					final int precision = castTarget.getPrecision() == null
+							? dialect.getDefaultDecimalPrecision()
+							: castTarget.getPrecision();
 					final int scale = castTarget.getScale() == null ? Size.DEFAULT_SCALE : castTarget.getScale();
 					return "decimal(" + precision + "," + scale + ")";
 				case "char":
 				case "varchar":
 				case "nchar":
 				case "nvarchar":
-					return castTarget.getLength() == null
-							? "char"
-							: ( "char(" + castTarget.getLength() + ")" );
+					if ( castTarget.getLength() == null ) {
+						// TODO: this is ugly and fragile, but could easily be handled in a DdlType
+						if ( castTarget.getJdbcMapping().getJdbcJavaType().getJavaType() == Character.class ) {
+							return "char(1)";
+						}
+						else {
+							return "char";
+						}
+					}
+					return "char(" + castTarget.getLength() + ")";
 				case "binary":
 				case "varbinary":
 					return castTarget.getLength() == null
 						? "binary"
-						: ( "binary(" + castTarget.getLength() + ")" );
+						: "binary(" + castTarget.getLength() + ")";
 			}
 		}
 		return sqlType;

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

@@ -5746,20 +5746,20 @@ else if ( isParameter( expression ) ) {
 				renderCasted( expression );
 			}
 		}
-		else if ( expression instanceof CaseSimpleExpression ) {
-			visitCaseSimpleExpression( (CaseSimpleExpression) expression, true );
+		else if ( expression instanceof CaseSimpleExpression caseSimpleExpression ) {
+			visitCaseSimpleExpression( caseSimpleExpression, true );
 		}
-		else if ( expression instanceof CaseSearchedExpression ) {
-			visitCaseSearchedExpression( (CaseSearchedExpression) expression, true );
+		else if ( expression instanceof CaseSearchedExpression caseSearchedExpression ) {
+			visitCaseSearchedExpression( caseSearchedExpression, true );
 		}
 		else {
 			renderExpressionAsClauseItem( expression );
 		}
 	}
 
 	protected void renderCasted(Expression expression) {
-		if ( expression instanceof SqmParameterInterpretation ) {
-			expression = ( (SqmParameterInterpretation) expression ).getResolvedExpression();
+		if ( expression instanceof SqmParameterInterpretation parameterInterpretation ) {
+			expression = parameterInterpretation.getResolvedExpression();
 		}
 		final List<SqlAstNode> arguments = new ArrayList<>( 2 );
 		arguments.add( expression );
@@ -5935,8 +5935,8 @@ assert getStatementStack().getCurrent() instanceof UpdateStatement
 		processNestedTableGroupJoins( tableGroup, null );
 		processTableGroupJoins( tableGroup );
 		ModelPartContainer modelPart = tableGroup.getModelPart();
-		if ( modelPart instanceof EntityPersister ) {
-			String[] querySpaces = (String[]) ( (EntityPersister) modelPart ).getQuerySpaces();
+		if ( modelPart instanceof EntityPersister persister ) {
+			final String[] querySpaces = (String[]) persister.getQuerySpaces();
 			for ( int i = 0; i < querySpaces.length; i++ ) {
 				registerAffectedTable( querySpaces[i] );
 			}
@@ -6113,7 +6113,7 @@ else if ( referenceJoinIndexForPredicateSwap == TableGroupHelper.NO_TABLE_GROUP_
 
 		ModelPartContainer modelPart = tableGroup.getModelPart();
 		if ( modelPart instanceof EntityPersister persister ) {
-			String[] querySpaces = (String[]) persister.getQuerySpaces();
+			final String[] querySpaces = (String[]) persister.getQuerySpaces();
 			for ( int i = 0; i < querySpaces.length; i++ ) {
 				registerAffectedTable( querySpaces[i] );
 			}

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/FunctionTests.java

@@ -1131,7 +1131,6 @@ public void testCastFunctionHexToBinary(SessionFactoryScope scope) {
 
 	@Test
 	@SkipForDialect( dialectClass = AltibaseDialect.class, reason = "Altibase cast to char does not do truncatation")
-	@SkipForDialect( dialectClass = MySQLDialect.class, matchSubTypes = true, reason = "MySQL cast does not do truncatation")
 	public void testCastFunctionWithLength(SessionFactoryScope scope) {
 		scope.inTransaction(
 				session -> {
@@ -1140,9 +1139,18 @@ public void testCastFunctionWithLength(SessionFactoryScope scope) {
 					assertEquals( 'A',
 							session.createQuery("select cast('ABCDEF' as Character)", Character.class)
 									.getSingleResult() );
+					assertEquals( ' ',
+							session.createQuery("select cast(' X ' as Character)", Character.class)
+									.getSingleResult() );
 					assertEquals( "ABC",
 							session.createQuery("select cast('ABCDEF' as String(3))", String.class)
 									.getSingleResult() );
+					assertEquals( "ABC",
+							session.createQuery("select cast('ABC' as String(6))", String.class)
+									.getSingleResult() );
+					assertEquals( "ABC ",
+							session.createQuery("select cast('ABC DEF' as String(4))", String.class)
+									.getSingleResult() );
 				}
 		);
 	}