Implement "RESTRICT" foreign key constraint in Wt::Dbo module

src/Wt/Dbo/Field.h

@@ -16,11 +16,13 @@ namespace Wt {
     template <class C> class collection;
 
     namespace Impl {
-const int FKNotNull = 0x01;
-const int FKOnUpdateCascade = 0x02;
-const int FKOnUpdateSetNull = 0x04;
-const int FKOnDeleteCascade = 0x08;
-const int FKOnDeleteSetNull = 0x10;
+const int FKNotNull          = 0x01;
+const int FKOnUpdateCascade  = 0x02;
+const int FKOnUpdateSetNull  = 0x04;
+const int FKOnUpdateRestrict = 0x08;
+const int FKOnDeleteCascade  = 0x10;
+const int FKOnDeleteSetNull  = 0x20;
+const int FKOnDeleteRestrict = 0x40;
     }
 
 /*! \brief Type that indicates one or more foreign key constraints.
@@ -31,8 +33,10 @@ const int FKOnDeleteSetNull = 0x10;
  * \sa \link Wt::Dbo::NotNull NotNull\endlink
  * \sa \link Wt::Dbo::OnUpdateCascade OnUpdateCascade\endlink,
  *     \link Wt::Dbo::OnUpdateSetNull OnUpdateSetNull\endlink
+ *     \link Wt::Dbo::OnUpdateRestrict OnUpdateRestrict\endlink
  * \sa \link Wt::Dbo::OnDeleteCascade OnDeleteCascade\endlink
  *     \link Wt::Dbo::OnDeleteSetNull OnDeleteSetNull\endlink
+ *     \link Wt::Dbo::OnDeleteRestrict OnDeleteRestrict\endlink
  *
  * \sa belongsTo(), hasMany()
  *
@@ -105,6 +109,23 @@ const ForeignKeyConstraint OnUpdateSetNull;
 const ForeignKeyConstraint OnUpdateSetNull(Impl::FKOnUpdateSetNull);
 #endif
 
+/*! \brief A constraint that restricts updates.
+ *
+ * A database constraint which restricts updates to the natural primary key
+ * in the referenced table.
+ *
+ * \note This constraint only affects the database schema creation. Currently
+ *       it is not possible to update a natural Id of an already saved object
+ *       through %Dbo itself.
+ *
+ * \ingroup dbo
+ */
+#ifdef DOXYGEN_ONLY
+const ForeignKeyConstraint OnUpdateRestrict;
+#else
+const ForeignKeyConstraint OnUpdateRestrict(Impl::FKOnUpdateRestrict);
+#endif
+
 /*! \brief A constraint that cascades deletes.
  *
  * A database constraint which propagates deletes of the referenced object
@@ -135,6 +156,21 @@ const ForeignKeyConstraint OnDeleteSetNull;
 const ForeignKeyConstraint OnDeleteSetNull(Impl::FKOnDeleteSetNull);
 #endif
 
+/*! \brief A constraint that restricts deletes.
+ *
+ * A database constraint which restricts deletes of the referenced object
+ * to also restrict deletion of the objects that reference.
+ *
+ * \note This constraint only affects the database schema creation.
+ *
+ * \ingroup dbo
+ */
+#ifdef DOXYGEN_ONLY
+const ForeignKeyConstraint OnDeleteRestrict;
+#else
+const ForeignKeyConstraint OnDeleteRestrict(Impl::FKOnDeleteRestrict);
+#endif
+
 class Session;
 class SqlStatement;
 

src/Wt/Dbo/Session.C

@@ -908,11 +908,16 @@ std::string Session::constraintString(Impl::MappingInfo *mapping,
   else if (field.fkConstraints() & Impl::FKOnUpdateSetNull
 	   && haveSupportUpdateCascade_)
     sql << " on update set null";
+  else if (field.fkConstraints() & Impl::FKOnUpdateRestrict
+           && haveSupportUpdateCascade_)
+    sql << " on update restrict";
 
   if (field.fkConstraints() & Impl::FKOnDeleteCascade)
     sql << " on delete cascade";
   else if (field.fkConstraints() & Impl::FKOnDeleteSetNull)
     sql << " on delete set null";
+  else if (field.fkConstraints() & Impl::FKOnDeleteRestrict)
+    sql << " on delete restrict";
 
   if (connection(false)->supportDeferrableFKConstraint()) //backend condition
     sql << " deferrable initially deferred";

test/dbo/DboTest8.C

@@ -0,0 +1,74 @@
+#define BOOST_TEST_MODULE Foreign Key Constraint
+
+#include <boost/test/included/unit_test.hpp>
+#include <Wt/Dbo/backend/Sqlite3.h>
+#include <Wt/Dbo/Dbo.h>
+#include <algorithm>
+
+namespace dbo = Wt::Dbo;
+
+class TableSrc1
+{
+    public:
+
+        template<typename Action>
+        void persist([[maybe_unused]] Action &a)
+        {
+        }
+};
+
+class TableSrc2
+{
+    public:
+
+        template<typename Action>
+        void persist([[maybe_unused]] Action &a)
+        {
+        }
+};
+
+class TableDst
+{
+    public:
+        dbo::ptr<TableSrc1> table_src1;
+        dbo::ptr<TableSrc2> table_src2;
+
+        template<typename Action>
+        void persist(Action &a)
+        {
+            dbo::belongsTo(a, table_src1, dbo::OnDeleteRestrict);
+            dbo::belongsTo(a, table_src2, dbo::OnUpdateRestrict);
+        }
+};
+
+BOOST_AUTO_TEST_CASE(foreign_key_constraints_test)
+{
+    dbo::Session session;
+    auto conn = std::make_unique<dbo::backend::Sqlite3>(":memory:");
+    session.setConnection(std::move(conn));
+
+    session.mapClass<TableSrc1>("table_src1");
+    session.mapClass<TableSrc2>("table_src2");
+    session.mapClass<TableDst>("table_dst");
+
+    auto sql = session.tableCreationSql();
+
+    std::string needle_del_restrict = "on delete restrict";
+    const auto it_del_restrict = std::search(begin(sql), end(sql), begin(needle_del_restrict), end(needle_del_restrict));
+    BOOST_REQUIRE((it_del_restrict != cend(sql)));
+
+    std::string needle_update_restrict = "on update restrict";
+    const auto it_update_restrict = std::search(begin(sql), end(sql), begin(needle_update_restrict), end(needle_update_restrict));
+    BOOST_REQUIRE((it_update_restrict != cend(sql)));
+
+    try
+    {
+        session.createTables();
+        BOOST_REQUIRE(true);
+    }
+    catch(...)
+    {
+        BOOST_REQUIRE(false);
+    }
+
+}