brotherton-erpnext/erpnext/patches/v11_0/update_total_qty_field.py

from __future__ import unicode_literals
import frappe

def execute():
	frappe.reload_doc('buying', 'doctype', 'purchase_order')
	frappe.reload_doc('buying', 'doctype', 'supplier_quotation')
	frappe.reload_doc('selling', 'doctype', 'sales_order')
	frappe.reload_doc('selling', 'doctype', 'quotation')
	frappe.reload_doc('stock', 'doctype', 'delivery_note')
	frappe.reload_doc('stock', 'doctype', 'purchase_receipt')
	frappe.reload_doc('accounts', 'doctype', 'sales_invoice')
	frappe.reload_doc('accounts', 'doctype', 'purchase_invoice')

	doctypes = ["Sales Order", "Sales Invoice", "Delivery Note",\
		"Purchase Order", "Purchase Invoice", "Purchase Receipt", "Quotation", "Supplier Quotation"]

	for doctype in doctypes:
		total_qty = frappe.db.sql('''
			SELECT
				parent, SUM(qty) as qty
			FROM
				`tab{0} Item`
			where parenttype = '{0}'
			GROUP BY parent
		'''.format(doctype), as_dict = True)

		# Query to update total_qty might become too big, Update in batches
		# batch_size is chosen arbitrarily, Don't try too hard to reason about it
		batch_size = 100000
		for i in range(0, len(total_qty), batch_size):
			batch_transactions = total_qty[i:i + batch_size]

			# UPDATE with CASE for some reason cannot use PRIMARY INDEX,
			# causing all rows to be examined, leading to a very slow update

			# UPDATE with WHERE clause uses PRIMARY INDEX, but will lead to too many queries

			# INSERT with ON DUPLICATE KEY UPDATE uses PRIMARY INDEX
			# and can perform multiple updates per query
			# This is probably never used anywhere else as of now, but should be
			values = []
			for d in batch_transactions:
				values.append("({0}, {1})".format(frappe.db.escape(d.parent), d.qty))
			conditions = ",".join(values)
			frappe.db.sql("""
				INSERT INTO `tab{}` (name, total_qty) VALUES {}
				ON DUPLICATE KEY UPDATE name = VALUES(name), total_qty = VALUES(total_qty)
			""".format(doctype, conditions))