Add patch to update schedule date of submitted Purchase Orders
diff --git a/erpnext/patches/v8_11/set_schedule_date_for_purchase_order.py b/erpnext/patches/v8_11/set_schedule_date_for_purchase_order.py
new file mode 100644
index 0000000..3c733b1
--- /dev/null
+++ b/erpnext/patches/v8_11/set_schedule_date_for_purchase_order.py
@@ -0,0 +1,20 @@
+# Copyright (c) 2017, Frappe and Contributors
+# License: GNU General Public License v3. See license.txt
+
+from __future__ import unicode_literals
+import frappe
+
+def execute():
+	frappe.reload_doctype("Purchase Order")
+	frappe.reload_doctype("Purchase Order Item")
+
+	if not frappe.db.has_column("Purchase Order", "schedule_date"):
+		return
+
+	#Update only submitted PO
+	for po in frappe.get_all("Purchase Order", filters= [["docstatus", "=", 1]], fields=["name"]):
+		purchase_order = frappe.get_doc("Purchase Order", po)
+		if purchase_order.items:
+			if not purchase_order.schedule_date:
+				purchase_order.schedule_date = purchase_order.items[0].schedule_date
+				purchase_order.save()
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