[FIX] core,account: avoid useless recomputations in res.config

User may use Settings menu just to click "Manage Users" buttons. Such simple
navigation sends ``create`` request, which may trigger a chain of
recomputations. To avoid that we redefine ``create`` method to check if a value
is really changed.

The previous explicit implementation lacks in v14 two fields at least:

* from module `account`
    ```
    qr_code = fields.Boolean(string='Display SEPA QR-code', related='company_id.qr_code', readonly=False)
    ```

* from module `enterprise/account_reports`
    ```
    account_tax_fiscal_country_id = fields.Many2one(string="Fiscal Country", related="company_id.account_tax_fiscal_country_id", readonly=False)
    ```

Performance Tests
=================

In this test we click "Manage users" and check stats for
``res.config.settings/create`` request.

Demo database with eCommerce and Accounting app installed:

```
|        | Number of queries | Query time, sec | Remaining time, sec |
|--------+-------------------+-----------------+---------------------|
| Before |               707 |           0.325 |               0.215 |
| After  |               382 |           0.283 |               0.174 |
```

The same, but with extra 1400 invoices:

```
|        | Number of queries | Query time, sec | Remaining time, sec |
|--------+-------------------+-----------------+---------------------|
| Before |               715 |           0.459 |               0.349 |
| After  |               382 |           0.176 |               0.107 |
```

---

opw-2489335

closes odoo/odoo#68486

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

1 files changed, 32 insertions, 0 deletions

diff --git a/odoo/addons/base/models/res_config.py b/odoo/addons/base/models/res_config.py
index fd9ddec2693..1abaf76663e 100644
--- a/odoo/addons/base/models/res_config.py
+++ b/odoo/addons/base/models/res_config.py
@@ -749,3 +749,35 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
         if (action_id):
             return RedirectWarning(msg % values, action_id, _('Go to the configuration panel'))
         return UserError(msg % values)
+
+    @api.model
+    def create(self, values):
+        # Optimisation: saving a res.config.settings even without changing any
+        # values will trigger the write of all related values. This in turn may
+        # trigger chain of further recomputation. To avoid it, delete values
+        # that were not changed.
+        for field in self._fields.values():
+            if not (field.name in values and field.related and not field.readonly):
+                continue
+            # we write on a related field like
+            # qr_code = fields.Boolean(related='company_id.qr_code', readonly=False)
+            fname0 = field.related[0]
+            if fname0 not in values:
+                continue
+
+            # determine the current value
+            field0 = self._fields[fname0]
+            old_value = field0.convert_to_record(
+                field0.convert_to_cache(values[fname0], self), self)
+            for fname in field.related[1:]:
+                old_value = next(iter(old_value), old_value)[fname]
+
+            # determine the new value
+            new_value = field.convert_to_record(
+                field.convert_to_cache(values[field.name], self), self)
+
+            # drop if the value is the same
+            if old_value == new_value:
+                values.pop(field.name)
+
+        return super(ResConfigSettings, self).create(values)