#32555: DecimalField Rounding inconsistency (PostgreSQL)
-------------------------------------+-------------------------------------
     Reporter:  bluppfisk            |                    Owner:  nobody
         Type:  Bug                  |                   Status:  closed
    Component:  Database layer       |                  Version:  2.2
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:  duplicate
     Keywords:  decimalfield,        |             Triage Stage:
  rounding, float                    |  Unreviewed
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------

Comment (by bluppfisk):

 I agree that is related, but even as I imitate Django's behaviour by using
 its own field and field configuration, the rounding is correct. It is only
 when I leave it fully up to Django that the rounding error happens.

 {{{
 def _normalize_positions(self):
         decimal_field = self._meta.get_field('positions').base_field
         self.positions = [
             decimal_field.context.create_decimal_from_float(val)
             .quantize(Decimal("1").scaleb(-decimal_field.decimal_places),
             context=decimal_field.context)
             for val in self.positions
         ]
 }}}

 > [Decimal('6586.878'), Decimal('0.204'), Decimal('0.715')]

 This is good.

 What is Django doing differently than me? It would seem logical that
 Django takes care of the normalising in a reproducible way.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/32555#comment:2>
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