Hi,

Nested loops in the code you provided could cause performance problems, especially if you have a lot of pickings and purchase orders. By removing nested loops and using Odoo's recordset operations, we can optimize the code as below.

from odoo import models, fields, api

class CreateBillFromPicking(models.Model):
    _inherit = 'stock.picking'

    def button_validate(self):
        res = super(CreateBillFromPicking, self).button_validate()
        purchase_orders = self.env['purchase.order'].search([('name', '=', self.origin)])
        done_pickings = self.filtered(lambda p: p.state == 'done')
        related_purchase_orders = purchase_orders.filtered(lambda po: done_pickings in po.picking_ids)
       
        for purchase_order in related_purchase_orders:
            purchase_order.action_create_invoice()
            invoices = self.env['account.move'].search([('purchase_id', '=', purchase_order.id)])
            invoices.write({'invoice_date': fields.Date.today()})
        return res

Hope it helps