On large recordsets I got some severe performance issues while browsing through an inherits relation.
For example I have a batch process exporting a csv file with products variants:

I have to export 50.000 products.

If I do :
`variant.categ_id` It takes a very long time to get the result.

If I do:
`variant.product_tmpl_id.categ_id` The result is immediate

The problem is that the global perfomance of the application is impacted by this problem.

For example my POS takes more than 15 minutes to load. Because I have 26.000 products and the compute price method uses a lot browsing through the inherits such like `product.cated_id`, `product.uom_id` and they all takes a huge time to compute.

Same issue in this case.

If I do :
`variant.price` It takes a very long time to get the result.

If I do:
`variant.product_tmpl_id.price` The result is immediate

Could you help me ?


Simple way to reproduce:

1/ Create a new database and install sale module
2/ Launch following script through odoo shell :

```python
# -*- coding: utf-8 -*-
import logging

_logger = logging.getLogger(__name__)
self = self  # noqa

nb_product = 50000

i = 0
while i < nb_product:
    prod = self.env['product.template'].create({'name': 'product_%s' % i})
    i += 1
    if i % 1000 == 0:
        self.env.cr.commit()
        _logger.info("%s Products Created" % i)
```

2/ Launch following script through odoo shell :
```python
# -*- coding: utf-8 -*-
import logging

_logger = logging.getLogger(__name__)
self = self  # noqa


products = self.env['product.product'].search([])

for product in products:
    # Immediate response
    _logger.info('Category Template %s' % product.product_tmpl_id.categ_id)
    # Lagging response
    _logger.info('Category Variant %s' % product.categ_id) 
    break
```
odoo/models.py
""" Override this method to do specific things when a form view is
        opened. This method is invoked by :meth:`~default_get`.
        """
        pass
    @api.model_cr_context
    def _field_create(self):
        """ Reflect the models and its fields in the models 'ir.model' and
        'ir.model.fields'. Also create entries in 'ir.model.data' if the key
        'module' is passed to the context.
        """
        cr = self._cr
        
        params = {
            'model': self._name,
            'name': self._description,
            'info': next(cls.__doc__ for cls in type(self).mro() if cls.__doc__),
            'state': 'manual' if self._custom else 'base',
            'transient': self._transient,
        }
        cr.execute(""" UPDATE ir_model
                       SET name=%(name)s, info=%(info)s, transient=%(transient)s
                       WHERE model=%(model)s
                       RETURNING id """, params)
        if not cr.rowcount:
            cr.execute(""" INSERT INTO ir_model (model, name, info, state, transient)
                           VALUES (%(model)s, %(name)s, %(info)s, %(state)s, %(transient)s)
                           RETURNING id """, params)
        model = self.env['ir.model'].browse(cr.fetchone()[0])
        self._context['todo'].append((10, model.modified, [['name', 'info', 'transient']]))
        if self._module == self._context.get('module'):