HHH-11957 : DB2 substring method needs to be exposed in DB297Dialect

(cherry picked from commit 80937ee583)

hibernate-core/src/main/java/org/hibernate/dialect/DB297Dialect.java

@@ -6,11 +6,14 @@
  */
 package org.hibernate.dialect;
 
+import org.hibernate.dialect.function.DB2SubstringFunction;
+import org.hibernate.dialect.function.StandardSQLFunction;
 import org.hibernate.hql.spi.id.IdTableSupportStandardImpl;
 import org.hibernate.hql.spi.id.MultiTableBulkIdStrategy;
 import org.hibernate.hql.spi.id.global.GlobalTemporaryTableBulkIdStrategy;
 import org.hibernate.hql.spi.id.local.AfterUseAction;
 import org.hibernate.hql.spi.id.local.LocalTemporaryTableBulkIdStrategy;
+import org.hibernate.type.StandardBasicTypes;
 
 /**
  * An SQL dialect for DB2 9.7.
@@ -19,6 +22,11 @@ import org.hibernate.hql.spi.id.local.LocalTemporaryTableBulkIdStrategy;
  */
 public class DB297Dialect extends DB2Dialect {
 
+	public DB297Dialect() {
+		super();
+		registerFunction( "substring", new DB2SubstringFunction() );
+	}
+
 	@Override
 	public String getCrossJoinSeparator() {
 		// DB2 9.7 and later support "cross join"

hibernate-core/src/main/java/org/hibernate/dialect/function/DB2SubstringFunction.java

@@ -0,0 +1,51 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.dialect.function;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.hibernate.type.StandardBasicTypes;
+
+/**
+ * When "substring" function is used for DB2, this implementation of {@link StandardSQLFunction}
+ * will render "substr" or "substring", depending on the last argument being used. If the last
+ * argument is a string unit ("CODEUNITS16", "CODEUNITS32", or "OCTETS"), then the function
+ * will be rendered as "substring"; otherwise, it will be rendered as "substr".
+ * <p/>
+ * ANSI SQL-92 standard defines "substring" without string units, which is more similar to DB2's "substr",
+ * so it makes sense to use DB2's "substr" function when string units are not provided.
+ * <p/>
+ * Background: DB2 has both "substr" and "substring", which are different functions that are not
+ * interchangeable. Prior to DB2 11.1, DB2's "substring" function requires an argument for string
+ * units; without this argument, DB2 throws an exception. DB2's "substr" function throws an exception
+ * if string unit is provided as an argument.
+ *
+ * @author Gail Badner
+ */
+public class DB2SubstringFunction extends StandardSQLFunction {
+	private static final Set<String> possibleStringUnits = new HashSet<>(
+			Arrays.asList( "CODEUNITS16", "CODEUNITS32", "OCTETS" )
+	);
+
+	public DB2SubstringFunction() {
+		super( "substring", StandardBasicTypes.STRING  );
+	}
+
+	@Override
+	protected String getRenderedName(List arguments) {
+		final String lastArgument = (String) arguments.get( arguments.size() - 1 );
+		if ( lastArgument != null && possibleStringUnits.contains( lastArgument.toUpperCase() ) ) {
+			return getName();
+		}
+		else{
+			return "substr";
+		}
+	}
+}

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

@@ -86,7 +86,7 @@ public class StandardSQLFunction implements SQLFunction {
 	@Override
 	public String render(Type firstArgumentType, List arguments, SessionFactoryImplementor sessionFactory) {
 		final StringBuilder buf = new StringBuilder();
-		buf.append( name ).append( '(' );
+		buf.append( getRenderedName( arguments) ).append( '(' );
 		for ( int i = 0; i < arguments.size(); i++ ) {
 			buf.append( arguments.get( i ) );
 			if ( i < arguments.size() - 1 ) {
@@ -96,6 +96,10 @@ public class StandardSQLFunction implements SQLFunction {
 		return buf.append( ')' ).toString();
 	}
 
+	protected String getRenderedName(List arguments) {
+		return getName();
+	}
+
 	@Override
 	public String toString() {
 		return name;