Before this commit, in large database, openning a sale.order can take 3s.
Because in module sale_purchase_stock, _get_purchase_order use a On2many field : stock_move_ids, with inverse field group_id.
Now it takes 200 ms.
closesodoo/odoo#117738
X-original-commit: 5fc448e7f6dcce94fb89b23be29c4d38a525dd97
Signed-off-by: William Henrotin (whe) <whe@odoo.com>