From 499cdd57083da462eec0a66bf76be18a3c703101 Mon Sep 17 00:00:00 2001
From: Raphael Collet <rco@odoo.com>
Date: Thu, 22 Nov 2018 14:32:11 +0000
Subject: [FIX] fields: combine special values during onchange

Consider a many2one field `foo_id` on model `bar`, with an inverse one2many
field `bar_ids` on model `foo`.  During an onchange, the statement

    bar.foo_id = foo

puts a special value in cache to add `bar` to the value of `foo.bar_ids`
without explicitly reading `foo.bar_ids`.

Executing the above statement a second time, the cache of `foo.bar_ids` is no
longer empty.  This causes the actual value of `foo.bar_ids` to be read and
updated.  The issue is that this can be slow for large values of `foo.bar_ids`.

Avoid reading the value of the one2many field by handling the case where the
cache contains the special value: simply update the special value to take into
account the second assignment.

closes odoo/odoo#28982
---
 odoo/fields.py | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

(limited to 'odoo/fields.py')

diff --git a/odoo/fields.py b/odoo/fields.py
index 58f7dc67dcb..91cde531649 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -2019,6 +2019,26 @@ class Many2one(_Relational):
         return super(Many2one, self).convert_to_onchange(value, record, names)
 
 
+class _RelationalMultiUpdate(object):
+    """ A getter to update the value of an x2many field, without reading its
+        value until necessary.
+    """
+    __slots__ = ['record', 'field', 'value']
+
+    def __init__(self, record, field, value):
+        self.record = record
+        self.field = field
+        self.value = value
+
+    def __call__(self):
+        # determine the current field's value, and update it in cache only
+        record, field, value = self.record, self.field, self.value
+        cache = record.env.cache
+        cache.remove(record, field)
+        val = field.convert_to_cache(record[field.name] | value, record, validate=False)
+        cache.set(record, field, val)
+        return val
+
 
 class _RelationalMulti(_Relational):
     """ Abstract class for relational fields *2many. """
@@ -2030,21 +2050,16 @@ class _RelationalMulti(_Relational):
         """ Update the cached value of ``self`` for ``records`` with ``value``. """
         cache = records.env.cache
         for record in records:
-            if cache.contains(record, self):
+            special = cache.get_special(record, self)
+            if isinstance(special, _RelationalMultiUpdate):
+                # include 'value' in the existing _RelationalMultiUpdate; this
+                # avoids reading the field's value (which may be large)
+                special.value |= value
+            elif cache.contains(record, self):
                 val = self.convert_to_cache(record[self.name] | value, record, validate=False)
                 cache.set(record, self, val)
             else:
-                cache.set_special(record, self, self._update_getter(record, value))
-
-    def _update_getter(self, record, value):
-        def getter():
-            # determine the current field's value, and update it in cache only
-            cache = record.env.cache
-            cache.remove(record, self)
-            val = self.convert_to_cache(record[self.name] | value, record, validate=False)
-            cache.set(record, self, val)
-            return val
-        return getter
+                cache.set_special(record, self, _RelationalMultiUpdate(record, self, value))
 
     def convert_to_cache(self, value, record, validate=True):
         # cache format: tuple(ids)
-- 
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