[IMP] core: remove `Field._slots`

This optimization is no longer necessary.  Thanks to Python 3.6's new
implementation of dicts, the memory footprint difference between slots
and dicts is now around 5%, which is no longer worth the complexity and
performance cost.

This saves 2% of the total installation time.

X-original-commit: c7f17770803744cbbb741fc11265ee914641aed7

1 files changed, 3 insertions, 3 deletions

diff --git a/addons/base_sparse_field/models/fields.py b/addons/base_sparse_field/models/fields.py
index 199bc9c3494..94242297180 100644
--- a/addons/base_sparse_field/models/fields.py
+++ b/addons/base_sparse_field/models/fields.py
@@ -32,6 +32,7 @@ fields.Field.__doc__ += """
         :param sparse: the name of the field where the value of this field must
             be stored.
 """
+fields.Field.sparse = None
 
 @monkey_patch(fields.Field)
 def _get_attrs(self, model, name):
@@ -76,11 +77,10 @@ def _inverse_sparse(self, records):
 class Serialized(fields.Field):
     """ Serialized fields provide the storage for sparse fields. """
     type = 'serialized'
-    _slots = {
-        'prefetch': False,              # not prefetched by default
-    }
     column_type = ('text', 'text')
 
+    prefetch = False                    # not prefetched by default
+
     def convert_to_column(self, value, record, values=None, validate=True):
         return self.convert_to_cache(value, record, validate=validate)