From 4e527d0f3ed35a2eb1daf8e5f85450478d5e9a2b Mon Sep 17 00:00:00 2001
From: Andrew Clemons <andrew.clemons@sap.com>
Date: Tue, 29 Oct 2013 07:48:55 +1300
Subject: [PATCH] HHH-8228 - enable foreign keys in HANA dialects by defaulting
 to 'ON UPDATE CASCADE'

---
 .../dialect/AbstractHANADialect.java          | 28 ++++++-------------
 .../dialect/HANARowStoreDialect.java          |  2 +-
 2 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/AbstractHANADialect.java b/hibernate-core/src/main/java/org/hibernate/dialect/AbstractHANADialect.java
index 41cf9f183f..6975d924f9 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/AbstractHANADialect.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/AbstractHANADialect.java
@@ -63,12 +63,10 @@ import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;
 /**
  * An abstract base class for HANA dialects. <br/>
  * <a href="http://help.sap.com/hana/html/sqlmain.html">SAP HANA Reference</a> <br/>
- * 
- * NOTE: This dialect is currently configured to <b>not</b> create foreign keys by
- * returning the empty string from {@link #getAddForeignKeyConstraintString} since they currently have caveats compared
- * to other databases. This does not
- * affect using this dialect with your own DDL scripts which use foreign keys.
- * 
+ *
+ * NOTE: This dialect is currently configured to create foreign keys with
+ * <code>on update cascade</code>.
+ *
  * @author Andrew Clemons <andrew.clemons@sap.com>
  */
 public abstract class AbstractHANADialect extends Dialect {
@@ -574,14 +572,6 @@ public abstract class AbstractHANADialect extends Dialect {
 		return false;
 	}
 
-	@Override
-	public boolean supportsCascadeDelete() {
-		// HANA does support cascade deletes, but since we have (temporarily) overridden the foreign key support,
-		// this should also be false.
-		// TODO: Enable once FK support is solidified and getAddForeignKeyConstraintString is corrected.
-		return false;
-	}
-
 	@Override
 	public ScrollMode defaultScrollMode() {
 		return ScrollMode.FORWARD_ONLY;
@@ -673,14 +663,14 @@ public abstract class AbstractHANADialect extends Dialect {
 	}
 
 	/**
-	 * Currently disabling foreign key creation when using Hibernate's auto-ddl
-	 * feature. HANA does allow creating foreign keys, but currently they do not always
-	 * behave as expected.
+	 * The default behaviour for 'on update restrict' on HANA is currently
+	 * to not allow any updates to any column of a row if the row has a 
+	 * foreign key. Make the default for foreign keys have 'on update cascade'
+	 * to work around the issue.
 	 */
 	@Override
 	public String getAddForeignKeyConstraintString(final String constraintName, final String[] foreignKey,
 			final String referencedTable, final String[] primaryKey, final boolean referencesPrimaryKey) {
-		// TODO: Re-evaluate in a later HANA release where, hopefully, this has been solidified.
-		return "";
+		return super.getAddForeignKeyConstraintString(constraintName, foreignKey, referencedTable, primaryKey, referencesPrimaryKey) + " on update cascade";
 	}
 }
diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/HANARowStoreDialect.java b/hibernate-core/src/main/java/org/hibernate/dialect/HANARowStoreDialect.java
index c17b6eb564..7aa5883e5e 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/HANARowStoreDialect.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/HANARowStoreDialect.java
@@ -31,7 +31,7 @@ package org.hibernate.dialect;
  * @author Andrew Clemons <andrew.clemons@sap.com>
  */
 public class HANARowStoreDialect extends AbstractHANADialect {
-	
+
 	// Even though it's currently pointless, provide this structure in case HANA row store merits additional
 	// differences in the future.