3

When using the Avg aggregate for a models.DecimalField, the returned value is a float, instead of a decimal.Decimal. Is this because my specific database (in this case sqlite3) doesn't support aggregate values as decimals? If so, are there databases that do? Is there a way around this (ie, a way to get the value back as a decimal), so that accurate decimal math can be done (also, without converting the float to a str and then back to a decimal.Decimal)?

Note: I'm not trolling for fights with people who believe that "accurate enough" is the same as "accurate", or flame baiting for discussions about the Star Ship Enterprise crashing due to erroneous, float-based arithmetic.

orokusaki
  • 55,146
  • 59
  • 179
  • 257

1 Answers1

1

From the SQLLite 3 manual, supported data types are null, integer, real (effectively float), text, or blob. Based on this I'd expect the engine to cast any input decimal.Decimal into a real then return it as a float to you, since it wouldn't want to upcast it past it's accuracy.

Most actual databases (I'd hardly consider sqllite for anything more than a prototype) support decimal data types. I know MySQL does. As to whether or not they return decimal.Decimal rather than float, I couldn't tell you unfortunately as I haven't done the investigation into their accuracy, float has been good enough for me. It'd be a good place to start though.

Michael Pratt
  • 3,438
  • 1
  • 17
  • 31