How to convert/migrate DateProperty to DateTimeProperty

Question

I know the difference between DateProperty and DateTimeProperty

difference between DateProperty and DateTimeProperty

I also appreciate how I could maintain my Schema (particularly missing values for properties) with tasks

https://stackoverflow.com/a/2019882/1175496

But I have a Model with date_filed=db.DateProperty I find I almost always want the (time) accuracy of db.DateTimeProperty How can I convert this field from DateTime to DateTimeProperty?

My questions are:

• How to do it
  • ie simply change from date_filed=db.DateProperty to date_filed=db.DateTimeProperty
• Will it somehow update existing entities automatically?
  • ie or must I create a task to change them?
• If entities with have different types for same properties, how does filtering and ordering on that property work?
  • ie DateProperty to a datetime.datetime value
  • ie

When a query involves a property with values of mixed types, the Datastore uses a deterministic ordering based on the internal representations: ...

2. Fixed-point numbers
   • Integers
   • Dates and times

• What are some outcomes / pitfalls
  • ie Validation Errors

Answer 1

I experimented with the simplest option, anticipated in the question. Also anticipated by the db.Model designers, it would seem (i.e. easy to do!)

• How to do it
  • Yes: simply change from date_filed=db.DateProperty to date_filed=db.DateTimeProperty
• Will it somehow update existing entities automatically?
  • Kind of: Specifically DateProperty.get_value_for_datastore method actually converts any datetime.date object to a datetime.datetime object before storing it as a "raw value" in the database.
  • Existing entities aren't really updated automatically, they just start using DateTimeProperty.make_value_from_datastore, (the opposite of get_value_for_datastore) which falls back to Property.make_value_from_datastore, which returns the raw value; the datetime.datetime object; not "truncating" it to a datetime.date object
  • No need to : ...create a task to change them
• If entities with have different types for same properties, how does filtering and ordering on that property work?
  • Irrelevant in this case; they have the same underlying type.
  • Although the "deterministic ordering based on internal representations" statement, which lists dates and datetimes both at the same bullet, suggests they have a common internal representation so they're comparable for ordering/filtering, etc.
• What are some outcomes / pitfalls
  • None encountered in this case; maybe someone has stories of other datatype migrations/conversions?