Avoid touching DB records when dry-run importing

just in case storage engine doesn't support transactions!

rattail_corepos/corepos/importing/db/model.py

@@ -43,8 +43,39 @@ class ToCore(importing.ToSQLAlchemy):
     """
     Base class for all CORE "operational" model importers.
     """
-    # TODO: should we standardize on the 'id' primary key? (can we even?)
-    # key = 'id'
+
+    def create_object(self, key, host_data):
+
+        # NOTE! some tables in CORE DB may be using the MyISAM storage engine,
+        # which means it is *not* transaction-safe and therefore we cannot rely
+        # on "rollback" if in dry-run mode!  in other words we better not touch
+        # the record at all, for dry run
+        if self.dry_run:
+            return host_data
+
+        return super(ToCore, self).create_object(key, host_data)
+
+    def update_object(self, obj, host_data, **kwargs):
+
+        # NOTE! some tables in CORE DB may be using the MyISAM storage engine,
+        # which means it is *not* transaction-safe and therefore we cannot rely
+        # on "rollback" if in dry-run mode!  in other words we better not touch
+        # the record at all, for dry run
+        if self.dry_run:
+            return obj
+
+        return super(ToCore, self).update_object(obj, host_data, **kwargs)
+
+    def delete_object(self, obj):
+
+        # NOTE! some tables in CORE DB may be using the MyISAM storage engine,
+        # which means it is *not* transaction-safe and therefore we cannot rely
+        # on "rollback" if in dry-run mode!  in other words we better not touch
+        # the record at all, for dry run
+        if self.dry_run:
+            return True
+
+        return super(ToCore, self).delete_object(obj)
 
 
 class ToCoreTrans(importing.ToSQLAlchemy):