From d45fa14fbece47cecf91d32caf7daa75a84c084b Mon Sep 17 00:00:00 2001
From: Christian Beikov <christian.beikov@gmail.com>
Date: Fri, 18 Jul 2025 09:24:25 +0200
Subject: [PATCH] HHH-19621 Don't render code units for DB2 for i

---
 .../community/dialect/DB2iLegacyDialect.java         | 10 ++++++++--
 .../main/java/org/hibernate/dialect/DB2iDialect.java | 12 ++++++++++++
 .../dialect/function/DB2SubstringFunction.java       |  9 ++++++++-
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2iLegacyDialect.java b/hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2iLegacyDialect.java
index 94d2c3aed20a..c452a3b95fd4 100644
--- a/hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2iLegacyDialect.java
+++ b/hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2iLegacyDialect.java
@@ -7,6 +7,7 @@
 import org.hibernate.boot.model.FunctionContributions;
 import org.hibernate.dialect.DatabaseVersion;
 import org.hibernate.dialect.function.CommonFunctionFactory;
+import org.hibernate.dialect.function.DB2SubstringFunction;
 import org.hibernate.dialect.identity.DB2IdentityColumnSupport;
 import org.hibernate.dialect.identity.DB2zIdentityColumnSupport;
 import org.hibernate.dialect.identity.IdentityColumnSupport;
@@ -57,9 +58,14 @@ public DB2iLegacyDialect(DatabaseVersion version) {
 
 	@Override
 	public void initializeFunctionRegistry(FunctionContributions functionContributions) {
-		super.initializeFunctionRegistry(functionContributions);
+		super.initializeFunctionRegistry( functionContributions );
+		// DB2 for i doesn't allow code units: https://www.ibm.com/docs/en/i/7.1.0?topic=functions-substring
+		functionContributions.getFunctionRegistry().register(
+				"substring",
+				new DB2SubstringFunction( false, functionContributions.getTypeConfiguration() )
+		);
 		if ( getVersion().isSameOrAfter( 7, 2 ) ) {
-			CommonFunctionFactory functionFactory = new CommonFunctionFactory(functionContributions);
+			CommonFunctionFactory functionFactory = new CommonFunctionFactory( functionContributions );
 			functionFactory.listagg( null );
 			functionFactory.inverseDistributionOrderedSetAggregates();
 			functionFactory.hypotheticalOrderedSetAggregates_windowEmulation();
diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/DB2iDialect.java b/hibernate-core/src/main/java/org/hibernate/dialect/DB2iDialect.java
index f3172739b474..a019837b7a26 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/DB2iDialect.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/DB2iDialect.java
@@ -6,6 +6,8 @@
 
 import jakarta.persistence.Timeout;
 import org.hibernate.Timeouts;
+import org.hibernate.boot.model.FunctionContributions;
+import org.hibernate.dialect.function.DB2SubstringFunction;
 import org.hibernate.dialect.identity.DB2IdentityColumnSupport;
 import org.hibernate.dialect.identity.DB2zIdentityColumnSupport;
 import org.hibernate.dialect.identity.IdentityColumnSupport;
@@ -56,6 +58,16 @@ public DB2iDialect(DatabaseVersion version) {
 		super(version);
 	}
 
+	@Override
+	public void initializeFunctionRegistry(FunctionContributions functionContributions) {
+		super.initializeFunctionRegistry( functionContributions );
+		// DB2 for i doesn't allow code units: https://www.ibm.com/docs/en/i/7.1.0?topic=functions-substring
+		functionContributions.getFunctionRegistry().register(
+				"substring",
+				new DB2SubstringFunction( false, functionContributions.getTypeConfiguration() )
+		);
+	}
+
 	@Override
 	protected DatabaseVersion getMinimumSupportedVersion() {
 		return MINIMUM_VERSION;
diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/function/DB2SubstringFunction.java b/hibernate-core/src/main/java/org/hibernate/dialect/function/DB2SubstringFunction.java
index 8653831f64f0..1d8ca27519de 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/function/DB2SubstringFunction.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/function/DB2SubstringFunction.java
@@ -28,7 +28,13 @@
  */
 public class DB2SubstringFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
 
+	private final boolean needsCodeUnit;
+
 	public DB2SubstringFunction(TypeConfiguration typeConfiguration) {
+		this( true, typeConfiguration );
+	}
+
+	public DB2SubstringFunction(boolean needsCodeUnit, TypeConfiguration typeConfiguration) {
 		super(
 				"substring",
 				new ArgumentTypesValidator( StandardArgumentsValidators.between( 2, 4 ), STRING, INTEGER, INTEGER, FunctionParameterType.ANY ),
@@ -36,6 +42,7 @@ public DB2SubstringFunction(TypeConfiguration typeConfiguration) {
 						StandardBasicTypes.STRING ) ),
 				StandardFunctionArgumentTypeResolvers.invariant( typeConfiguration, STRING, INTEGER, INTEGER )
 		);
+		this.needsCodeUnit = needsCodeUnit;
 	}
 
 	@Override
@@ -51,7 +58,7 @@ public void render(
 			sqlAppender.appendSql( ',' );
 			arguments.get( i ).accept( walker );
 		}
-		if ( argumentCount != 4 ) {
+		if ( argumentCount != 4 && needsCodeUnit ) {
 			sqlAppender.appendSql( ",codeunits32" );
 		}
 		sqlAppender.appendSql( ')' );