[FIX] base: simplify computation of commercial_partner_id

The computation was using an SQL query to speed it up, but the recent
changes in the ORM have made this optimization useless.

We have benchmarked an import of 10000 partners linked to the same
parent, in a database with Sales and Stock installed.  The import is
slightly faster without the SQL query (7 min vs 8 min).

closes odoo/odoo#36768

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>

odoo/addons/base/models/res_partner.py

@@ -273,32 +273,8 @@ class Partner(models.Model):
 
     @api.depends('is_company', 'parent_id.commercial_partner_id')
     def _compute_commercial_partner(self):
-        self.env.cr.execute("""
-        WITH RECURSIVE cpid(id, parent_id, commercial_partner_id, final) AS (
-            SELECT
-                id, parent_id, id,
-                (coalesce(is_company, false) OR parent_id IS NULL) as final
-            FROM res_partner
-            WHERE id = ANY(%s)
-        UNION
-            SELECT
-                cpid.id, p.parent_id, p.id,
-                (coalesce(is_company, false) OR p.parent_id IS NULL) as final
-            FROM res_partner p
-            JOIN cpid ON (cpid.parent_id = p.id)
-            WHERE NOT cpid.final
-        )
-        SELECT cpid.id, cpid.commercial_partner_id
-        FROM cpid
-        WHERE final AND id = ANY(%s);
-        """, [self.ids, self.ids])
-
-        d = dict(self.env.cr.fetchall())
         for partner in self:
-            fetched = d.get(partner.id)
-            if fetched is not None:
-                partner.commercial_partner_id = fetched
-            elif partner.is_company or not partner.parent_id:
+            if partner.is_company or not partner.parent_id:
                 partner.commercial_partner_id = partner
             else:
                 partner.commercial_partner_id = partner.parent_id.commercial_partner_id