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
groupby_fields = [g['field'] for g in annotated_groupbys]
        order = orderby or ','.join([g for g in groupby_list])
        groupby_dict = {gb['groupby']: gb for gb in annotated_groupbys}
        self._apply_ir_rules(query, 'read')
        for gb in groupby_fields:
            assert gb in fields, "Fields in 'groupby' must appear in the list of fields to read (perhaps it's missing in the list view?)"
            assert gb in self._fields, "Unknown field %r in 'groupby'" % gb
            gb_field = self._fields[gb].base_field
            assert gb_field.store and gb_field.column_type, "Fields in 'groupby' must be regular database-persisted fields (no function or related fields), or function fields with store=True"
        aggregated_fields = [
            f for f in fields
            if f != 'sequence'
            if f not in groupby_fields
            for field in [self._fields.get(f)]
            if field
            if field.group_operator
            if field.base_field.store and field.base_field.column_type
        ]
        field_formatter = lambda f: (
            self._fields[f].group_operator,
            self._inherits_join_calc(self._table, f, query),
            f,
        )
        select_terms = ['%s(%s) AS "%s" ' % field_formatter(f) for f in aggregated_fields]
        for gb in annotated_groupbys:
            select_terms.append('%s as "%s" ' % (gb['qualified_field'], gb['groupby']))
        groupby_terms, orderby_terms = self._read_group_prepare(order, aggregated_fields, annotated_groupbys, query)
        from_clause, where_clause, where_clause_params = query.get_sql()
        if lazy and (len(groupby_fields) >= 2 or not self._context.get('group_by_no_leaf')):
            count_field = groupby_fields[0] if len(groupby_fields) >= 1 else '_'