## Impacted versions:
 8.0 / 9.0 / 10.0
## Steps to reproduce:
* see https://github.com/odoo/odoo/issues/11841
* in a shell
  1. create an in memory record `order = self.env['purcahse.order'].new({....})`
  2. create an in memory record with a reference to the first one `order_line = self.env['purchase.order.line'].new({'order_id': order, ....})`
  3. order_line.order_id is an in memory recordset
  4. create a record for a model that inherits from mail.thread `self.env['product.product'].create({....})`
  5. At this stage order_line.order_id is an empty recordset

## Current behavior:
 In memory records are dropped when a call is done to self.invalidate_cache
## Expected behavior:
In memory records are preserved when a call is done to self.invalidate_cache


There are lot of places where the method `invalidate_cache` is called and the silent removal of the in memory records from all environments has unpredictable effects on fields modified by a computed method or an onchange or even related fields .... Moreover since all caches are invalidated each time you create / write / unlink  (https://github.com/odoo/odoo/blob/10.0/addons/mail/models/mail_followers.py#L111) an instance of a model that inherits from 'mail.thread', the performances of the server are severely penalized.

OPW703903

addons/purchase/purchase.py
self.write(cr, uid, ids, {'state': 'done'}, context=context)
        self.set_order_line_status(cr, uid, ids, 'done', context=context)
    def action_invoice_create(self, cr, uid, ids, context=None):
        """Generates invoice for given ids of purchase orders and links that invoice ID to purchase order.
        :param ids: list of ids of purchase orders.
        :return: ID of created invoice.
        :rtype: int
        """
        context = dict(context or {})
        
        inv_obj = self.pool.get('account.invoice')
        inv_line_obj = self.pool.get('account.invoice.line')
        res = False
        uid_company_id = self.pool.get('res.users').browse(cr, uid, uid, context=context).company_id.id
        for order in self.browse(cr, uid, ids, context=context):
            context.pop('force_company', None)
            if order.company_id.id != uid_company_id:
                
                
                context['force_company'] = order.company_id.id
                order = self.browse(cr, uid, order.id, context=context)