[IMP] core: optimize read() by avoiding useless query

When the `select` returns nothing more than ids that are already known, there is
no need to make it at all.

This removes one query from `_read` every time it has to fetch only fields that
are stored in a different table (o2m, ...), which happens all the time when
reading a stored field first (triggering prefetch) and then reading a o2m.

The query that is now removed was used to check access rules, but the trick is
to use `check_access_rule` to verify the rules in python instead.

Part of task-2061122

closes odoo/odoo#36263

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/odoo/addons/test_new_api/tests/test_new_fields.py b/odoo/addons/test_new_api/tests/test_new_fields.py
index b98b1a34c0f..94b1dd9c04e 100644
--- a/odoo/addons/test_new_api/tests/test_new_fields.py
+++ b/odoo/addons/test_new_api/tests/test_new_fields.py
@@ -1714,6 +1714,53 @@ class TestFields(TransactionCaseWithUserDemo):
         self.assertEqual(record_no_bin_size.binary_computed, expected_value)
         self.assertEqual(record_bin_size.binary_computed, expected_value)
 
+    def test_96_ir_rule_m2m_field(self):
+        """Ensures m2m fields can't be read if the left records can't be read.
+        Also makes sure reading m2m doesn't take more queries than necessary."""
+        tag = self.env['test_new_api.multi.tag'].create({})
+        record = self.env['test_new_api.multi.line'].create({
+            'name': 'image',
+            'tags': [(4, tag.id)],
+        })
+
+        # only one query as admin: reading pivot table
+        with self.assertQueryCount(1):
+            record.read(['tags'])
+
+        user = self.env['res.users'].create({'name': "user", 'login': "user"})
+        record_user = record.with_user(user)
+
+        # prep the following query count by caching access check related data
+        record_user.read(['tags'])
+
+        # only one query as user: reading pivot table
+        with self.assertQueryCount(1):
+            record_user.read(['tags'])
+
+        # create a passing ir.rule
+        self.env['ir.rule'].create({
+            'model_id': self.env['ir.model']._get(record._name).id,
+            'domain_force': "[('id', '=', %d)]" % record.id,
+        })
+
+        # prep the following query count by caching access check related data
+        record_user.read(['tags'])
+
+        # still only 1 query: reading pivot table
+        # access rules are checked in python in this case
+        with self.assertQueryCount(1):
+            record_user.read(['tags'])
+
+        # create a blocking ir.rule
+        self.env['ir.rule'].create({
+            'model_id': self.env['ir.model']._get(record._name).id,
+            'domain_force': "[('id', '!=', %d)]" % record.id,
+        })
+
+        # ensure ir.rule is applied even when reading m2m
+        with self.assertRaises(AccessError):
+            record_user.read(['tags'])
+
 
 class TestX2many(common.TransactionCase):
     def test_definition_many2many(self):