HHH-18497 Add xmlconcat function

documentation/src/main/asciidoc/userguide/chapters/query/hql/QueryLanguage.adoc

@@ -2173,7 +2173,8 @@ it is necessary to enable the `hibernate.query.hql.xml_functions_enabled` config
 
 | `xmlelement()` | Constructs an XML element from arguments
 | `xmlcomment()` | Constructs an XML comment from the single argument
-| `xmlforest()` | Constructs an XML forest from thearguments
+| `xmlforest()` | Constructs an XML forest from the arguments
+| `xmlconcat()` | Concatenates multiple XML fragments to each other
 |===
 
 
@@ -2250,6 +2251,21 @@ include::{xml-example-dir-hql}/XmlForestTest.java[tags=hql-xmlforest-example]
 
 WARNING: SAP HANA, MySQL, MariaDB and HSQLDB do not support this function.
 
+[[hql-xmlconcat-function]]
+===== `xmlconcat()`
+
+Concatenates multiple XML fragments to each other.
+
+[[hql-xmlconcat-example]]
+====
+[source, java, indent=0]
+----
+include::{xml-example-dir-hql}/XmlConcatTest.java[tags=hql-xmlconcat-example]
+----
+====
+
+WARNING: SAP HANA, MySQL, MariaDB and HSQLDB do not support this function.
+
 [[hql-user-defined-functions]]
 ==== Native and user-defined functions
 

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2LegacyDialect.java

@@ -444,6 +444,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 	}
 
 	@Override

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/H2LegacyDialect.java

@@ -421,6 +421,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 			functionFactory.xmlelement_h2();
 			functionFactory.xmlcomment();
 			functionFactory.xmlforest_h2();
+			functionFactory.xmlconcat_h2();
 		}
 		else {
 			functionFactory.listagg_groupConcat();

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/OracleLegacyDialect.java

@@ -329,6 +329,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 	}
 
 	@Override

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/PostgreSQLLegacyDialect.java

@@ -672,6 +672,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 
 		if ( getVersion().isSameOrAfter( 9, 4 ) ) {
 			functionFactory.makeDateTimeTimestamp();

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/SQLServerLegacyDialect.java

@@ -416,6 +416,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement_sqlserver();
 		functionFactory.xmlcomment_sqlserver();
 		functionFactory.xmlforest_sqlserver();
+		functionFactory.xmlconcat_sqlserver();
 		if ( getVersion().isSameOrAfter( 14 ) ) {
 			functionFactory.listagg_stringAggWithinGroup( "varchar(max)" );
 			functionFactory.jsonArrayAgg_sqlserver( getVersion().isSameOrAfter( 16 ) );

hibernate-core/src/main/java/org/hibernate/dialect/DB2Dialect.java

@@ -429,6 +429,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java

@@ -356,6 +356,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement_h2();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest_h2();
+		functionFactory.xmlconcat_h2();
 	}
 
 	/**

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

@@ -419,6 +419,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 	}
 
 	@Override

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

@@ -633,6 +633,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement();
 		functionFactory.xmlcomment();
 		functionFactory.xmlforest();
+		functionFactory.xmlconcat();
 
 		functionFactory.makeDateTimeTimestamp();
 		// Note that PostgreSQL doesn't support the OVER clause for ordered set-aggregate functions

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

@@ -434,6 +434,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlelement_sqlserver();
 		functionFactory.xmlcomment_sqlserver();
 		functionFactory.xmlforest_sqlserver();
+		functionFactory.xmlconcat_sqlserver();
 		if ( getVersion().isSameOrAfter( 14 ) ) {
 			functionFactory.listagg_stringAggWithinGroup( "varchar(max)" );
 			functionFactory.jsonArrayAgg_sqlserver( getVersion().isSameOrAfter( 16 ) );

hibernate-core/src/main/java/org/hibernate/dialect/function/CommonFunctionFactory.java

@@ -153,10 +153,13 @@
 import org.hibernate.dialect.function.json.SQLServerJsonReplaceFunction;
 import org.hibernate.dialect.function.json.SQLServerJsonSetFunction;
 import org.hibernate.dialect.function.json.SQLServerJsonValueFunction;
+import org.hibernate.dialect.function.xml.H2XmlConcatFunction;
 import org.hibernate.dialect.function.xml.H2XmlElementFunction;
 import org.hibernate.dialect.function.xml.H2XmlForestFunction;
+import org.hibernate.dialect.function.xml.SQLServerXmlConcatFunction;
 import org.hibernate.dialect.function.xml.SQLServerXmlElementFunction;
 import org.hibernate.dialect.function.xml.SQLServerXmlForestFunction;
+import org.hibernate.dialect.function.xml.XmlConcatFunction;
 import org.hibernate.dialect.function.xml.XmlElementFunction;
 import org.hibernate.dialect.function.xml.XmlForestFunction;
 import org.hibernate.query.sqm.function.SqmFunctionRegistry;
@@ -4167,4 +4170,25 @@ public void xmlforest_h2() {
 	public void xmlforest_sqlserver() {
 		functionRegistry.register( "xmlforest", new SQLServerXmlForestFunction( typeConfiguration ) );
 	}
+
+	/**
+	 * Standard xmlconcat() function
+	 */
+	public void xmlconcat() {
+		functionRegistry.register( "xmlconcat", new XmlConcatFunction( typeConfiguration ) );
+	}
+
+	/**
+	 * H2 xmlconcat() function
+	 */
+	public void xmlconcat_h2() {
+		functionRegistry.register( "xmlconcat", new H2XmlConcatFunction( typeConfiguration ) );
+	}
+
+	/**
+	 * SQL Server xmlconcat() function
+	 */
+	public void xmlconcat_sqlserver() {
+		functionRegistry.register( "xmlconcat", new SQLServerXmlConcatFunction( typeConfiguration ) );
+	}
 }

hibernate-core/src/main/java/org/hibernate/dialect/function/xml/H2XmlConcatFunction.java

@@ -0,0 +1,39 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.dialect.function.xml;
+
+import java.util.List;
+
+import org.hibernate.query.ReturnableType;
+import org.hibernate.sql.ast.SqlAstTranslator;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.type.spi.TypeConfiguration;
+
+/**
+ * H2 xmlconcat function.
+ */
+public class H2XmlConcatFunction extends XmlConcatFunction {
+
+	public H2XmlConcatFunction(TypeConfiguration typeConfiguration) {
+		super( typeConfiguration );
+	}
+
+	@Override
+	public void render(
+			SqlAppender sqlAppender,
+			List<? extends SqlAstNode> sqlAstArguments,
+			ReturnableType<?> returnType,
+			SqlAstTranslator<?> walker) {
+		String separator = "";
+		sqlAppender.appendSql( '(' );
+		for ( SqlAstNode sqlAstArgument : sqlAstArguments ) {
+			sqlAppender.appendSql( separator );
+			sqlAstArgument.accept( walker );
+			separator = "||";
+		}
+		sqlAppender.appendSql( ')' );
+	}
+}

hibernate-core/src/main/java/org/hibernate/dialect/function/xml/SQLServerXmlConcatFunction.java

@@ -0,0 +1,41 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.dialect.function.xml;
+
+import java.util.List;
+
+import org.hibernate.query.ReturnableType;
+import org.hibernate.sql.ast.SqlAstTranslator;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.type.spi.TypeConfiguration;
+
+/**
+ * SQL Server xmlconcat function.
+ */
+public class SQLServerXmlConcatFunction extends XmlConcatFunction {
+
+	public SQLServerXmlConcatFunction(TypeConfiguration typeConfiguration) {
+		super( typeConfiguration );
+	}
+
+	@Override
+	public void render(
+			SqlAppender sqlAppender,
+			List<? extends SqlAstNode> sqlAstArguments,
+			ReturnableType<?> returnType,
+			SqlAstTranslator<?> walker) {
+		sqlAppender.appendSql( "cast" );
+		char separator = '(';
+		for ( SqlAstNode sqlAstArgument : sqlAstArguments ) {
+			sqlAppender.appendSql( separator );
+			sqlAppender.appendSql( "cast(" );
+			sqlAstArgument.accept( walker );
+			sqlAppender.appendSql( " as nvarchar(max))" );
+			separator = '+';
+		}
+		sqlAppender.appendSql( " as xml)" );
+	}
+}

hibernate-core/src/main/java/org/hibernate/dialect/function/xml/XmlConcatFunction.java

@@ -0,0 +1,58 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.dialect.function.xml;
+
+import java.util.List;
+
+import org.hibernate.query.ReturnableType;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
+import org.hibernate.query.sqm.function.FunctionKind;
+import org.hibernate.query.sqm.produce.function.ArgumentTypesValidator;
+import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
+import org.hibernate.query.sqm.produce.function.StandardFunctionArgumentTypeResolvers;
+import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
+import org.hibernate.sql.ast.SqlAstTranslator;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.type.SqlTypes;
+import org.hibernate.type.spi.TypeConfiguration;
+
+import static org.hibernate.query.sqm.produce.function.FunctionParameterType.XML;
+
+/**
+ * Standard XmlConcatFunction function.
+ */
+public class XmlConcatFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
+
+	public XmlConcatFunction(TypeConfiguration typeConfiguration) {
+		super(
+				"xmlconcat",
+				FunctionKind.NORMAL,
+				StandardArgumentsValidators.composite(
+						new ArgumentTypesValidator( StandardArgumentsValidators.min( 1 ), XML )
+				),
+				StandardFunctionReturnTypeResolvers.invariant(
+						typeConfiguration.getBasicTypeRegistry().resolve( String.class, SqlTypes.SQLXML )
+				),
+				StandardFunctionArgumentTypeResolvers.impliedOrInvariant( typeConfiguration, XML )
+		);
+	}
+
+	@Override
+	public void render(
+			SqlAppender sqlAppender,
+			List<? extends SqlAstNode> sqlAstArguments,
+			ReturnableType<?> returnType,
+			SqlAstTranslator<?> walker) {
+		sqlAppender.appendSql( "xmlconcat" );
+		char separator = '(';
+		for ( SqlAstNode sqlAstArgument : sqlAstArguments ) {
+			sqlAppender.appendSql( separator );
+			sqlAstArgument.accept( walker );
+			separator = ',';
+		}
+		sqlAppender.appendSql( ')' );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/criteria/HibernateCriteriaBuilder.java

@@ -4067,6 +4067,7 @@ default <E> JpaPredicate collectionOverlapsNullable(Collection<E> collection1, E
 	 * Creates an XML forest from the given XML element expressions.
 	 *
 	 * @since 7.0
+	 * @see #named(Expression, String)
 	 */
 	@Incubating
 	JpaExpression<String> xmlforest(Expression<?>... elements);
@@ -4075,10 +4076,27 @@ default <E> JpaPredicate collectionOverlapsNullable(Collection<E> collection1, E
 	 * Creates an XML forest from the given XML element expressions.
 	 *
 	 * @since 7.0
+	 * @see #named(Expression, String)
 	 */
 	@Incubating
 	JpaExpression<String> xmlforest(List<? extends Expression<?>> elements);
 
+	/**
+	 * Concatenates the given XML element expressions.
+	 *
+	 * @since 7.0
+	 */
+	@Incubating
+	JpaExpression<String> xmlconcat(Expression<?>... elements);
+
+	/**
+	 * Concatenates the given XML element expressions.
+	 *
+	 * @since 7.0
+	 */
+	@Incubating
+	JpaExpression<String> xmlconcat(List<? extends Expression<?>> elements);
+
 	/**
 	 * Creates a named expression. The name is important for the result of the expression,
 	 * e.g. when building an {@code xmlforest}, the name acts as the XML element name.

hibernate-core/src/main/java/org/hibernate/query/criteria/spi/HibernateCriteriaBuilderDelegate.java

@@ -3657,6 +3657,18 @@ public JpaExpression<String> xmlforest(List<? extends Expression<?>> elements) {
 		return criteriaBuilder.xmlforest( elements );
 	}
 
+	@Override
+	@Incubating
+	public JpaExpression<String> xmlconcat(Expression<?>... elements) {
+		return criteriaBuilder.xmlconcat( elements );
+	}
+
+	@Override
+	@Incubating
+	public JpaExpression<String> xmlconcat(List<? extends Expression<?>> elements) {
+		return criteriaBuilder.xmlconcat( elements );
+	}
+
 	@Override
 	@Incubating
 	public <T> JpaExpression<T> named(Expression<T> expression, String name) {

hibernate-core/src/main/java/org/hibernate/query/sqm/NodeBuilder.java

@@ -765,6 +765,12 @@ <T> SqmJsonValueExpression<T> jsonValue(
 	@Override
 	SqmExpression<String> xmlforest(Expression<?>... elements);
 
+	@Override
+	SqmExpression<String> xmlconcat(Expression<?>... elements);
+
+	@Override
+	SqmExpression<String> xmlconcat(List<? extends Expression<?>> elements);
+
 	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// Covariant overrides
 

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

@@ -5732,4 +5732,18 @@ public SqmExpression<String> xmlforest(List<? extends Expression<?>> elements) {
 				queryEngine
 		);
 	}
+
+	@Override
+	public SqmExpression<String> xmlconcat(Expression<?>... elements) {
+		return xmlconcat( Arrays.asList( elements ) );
+	}
+
+	@Override
+	public SqmExpression<String> xmlconcat(List<? extends Expression<?>> elements) {
+		return getFunctionDescriptor( "xmlforest" ).generateSqmExpression(
+				(List<? extends SqmTypedNode<?>>) elements,
+				null,
+				queryEngine
+		);
+	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/ArgumentTypesValidator.java

@@ -251,6 +251,8 @@ private static boolean isCompatible(FunctionParameterType type, JdbcType jdbcTyp
 			case SPATIAL -> jdbcType.isSpatial();
 			case JSON -> jdbcType.isJson();
 			case IMPLICIT_JSON -> jdbcType.isImplicitJson();
+			case XML -> jdbcType.isXml();
+			case IMPLICIT_XML -> jdbcType.isImplicitXml();
 			default -> true; // TODO: should we throw here?
 		};
 	}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/FunctionParameterType.java

@@ -98,6 +98,18 @@ public enum FunctionParameterType {
 	 * @since 7.0
 	 */
 	IMPLICIT_JSON,
+	/**
+	 * Indicates that the argument should be a XML type
+	 * @see org.hibernate.type.SqlTypes#isXmlType(int)
+	 * @since 7.0
+	 */
+	XML,
+	/**
+	 * Indicates that the argument should be a XML or String type
+	 * @see org.hibernate.type.SqlTypes#isImplicitXmlType(int)
+	 * @since 7.0
+	 */
+	IMPLICIT_XML,
 	/**
 	 * Indicates a parameter that accepts any type, except untyped expressions like {@code null} literals
 	 */

hibernate-core/src/main/java/org/hibernate/type/SqlTypes.java

@@ -1021,4 +1021,36 @@ public static boolean isImplicitJsonType(int typeCode) {
 				return isCharacterOrClobType( typeCode );
 		}
 	}
+
+	/**
+	 * Does the typecode represent a XML type.
+	 *
+	 * @param typeCode - a JDBC type code
+	 * @since 7.0
+	 */
+	public static boolean isXmlType(int typeCode) {
+		switch ( typeCode ) {
+			case SQLXML:
+			case XML_ARRAY:
+				return true;
+			default:
+				return false;
+		}
+	}
+
+	/**
+	 * Does the typecode represent an XML type or a type that can be implicitly cast to XML.
+	 *
+	 * @param typeCode - a JDBC type code
+	 * @since 7.0
+	 */
+	public static boolean isImplicitXmlType(int typeCode) {
+		switch ( typeCode ) {
+			case SQLXML:
+			case XML_ARRAY:
+				return true;
+			default:
+				return isCharacterOrClobType( typeCode );
+		}
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/jdbc/JdbcType.java

@@ -435,6 +435,16 @@ default boolean isImplicitJson() {
 		return isImplicitJsonType( getDefaultSqlTypeCode() );
 	}
 
+	@Incubating
+	default boolean isXml() {
+		return isXmlType( getDefaultSqlTypeCode() );
+	}
+
+	@Incubating
+	default boolean isImplicitXml() {
+		return isImplicitXmlType( getDefaultSqlTypeCode() );
+	}
+
 	@Incubating
 	default boolean isBoolean() {
 		return getDefaultSqlTypeCode() == BOOLEAN;

hibernate-core/src/test/java/org/hibernate/orm/test/function/xml/XmlConcatTest.java

@@ -0,0 +1,36 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.function.xml;
+
+import org.hibernate.cfg.QuerySettings;
+
+import org.hibernate.testing.orm.junit.DialectFeatureChecks;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.RequiresDialectFeature;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author Christian Beikov
+ */
+@DomainModel
+@SessionFactory
+@ServiceRegistry(settings = @Setting(name = QuerySettings.XML_FUNCTIONS_ENABLED, value = "true"))
+@RequiresDialectFeature( feature = DialectFeatureChecks.SupportsXmlconcat.class)
+public class XmlConcatTest {
+
+	@Test
+	public void testSimple(SessionFactoryScope scope) {
+		scope.inSession( em -> {
+			//tag::hql-xmlconcat-example[]
+			em.createQuery( "select xmlconcat(xmlelement(name e1, 123), xmlelement(name e2, 'text'))" ).getResultList();
+			//end::hql-xmlconcat-example[]
+		} );
+	}
+
+}

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

@@ -170,6 +170,23 @@ public void testXmlforest(SessionFactoryScope scope) {
 		);
 	}
 
+	@Test
+	@RequiresDialectFeature(feature = DialectFeatureChecks.SupportsXmlconcat.class)
+	public void testXmlconcat(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					Tuple tuple = session.createQuery(
+							"select xmlconcat(xmlelement(name e1, 123), xmlelement(name e2, 'text'))," +
+									"xmlconcat(xmlelement(name id, e.id), xmlelement(name theString, e.theString)) " +
+									"from EntityOfBasics e where e.id = 1",
+							Tuple.class
+					).getSingleResult();
+					assertXmlEquals( "<r><e1>123</e1><e2>text</e2></r>", "<r>" + tuple.get( 0, String.class ) + "</r>" );
+					assertXmlEquals( "<r><id>1</id><theString>Dog</theString></r>", "<r>" + tuple.get( 1, String.class ) + "</r>" );
+				}
+		);
+	}
+
 	private void assertXmlEquals(String expected, String actual) {
 		final Document expectedDoc = parseXml( xmlNormalize( expected ) );
 		final Document actualDoc = parseXml( xmlNormalize( actual ) );

hibernate-testing/src/main/java/org/hibernate/testing/orm/junit/DialectFeatureChecks.java

@@ -856,6 +856,12 @@ public boolean apply(Dialect dialect) {
 		}
 	}
 
+	public static class SupportsXmlconcat implements DialectFeatureCheck {
+		public boolean apply(Dialect dialect) {
+			return definesFunction( dialect, "xmlconcat" );
+		}
+	}
+
 	public static class IsJtds implements DialectFeatureCheck {
 		public boolean apply(Dialect dialect) {
 			return dialect instanceof SybaseDialect && ( (SybaseDialect) dialect ).getDriverKind() == SybaseDriverKind.JTDS;