Custom fields with naive_datetime type report difference in microseconds on tests


Hi everyone,

I added two custom fields with naive_datetime type to one of my schemas and even though everything seems right (inserting, loading data), when i run tests against it, it gives an error comparing values on microseconds (0 != 6).

An example of the difference:
lhs: %NaiveDateTime{calendar: Calendar.ISO, day: 10, hour: 0, minute: 0, month: 11, second: 0, year: 2018, microsecond: {0, 6}}
rhs: %NaiveDateTime{calendar: Calendar.ISO, day: 10, hour: 0, minute: 0, month: 11, second: 0, year: 2018, microsecond: {0, 0}}

I saw someone mentioning to add @timestamps_opts [usec: false] before your schema settings but that only applies to the timestamps fields AFAIK.

Am i missing something simple here ?

Note: I’m using Phoenix 1.3, Ecto 2.2, PostgreSQL as DB and creating simple fixtures functions on the tests.

Thank you


IIRC (and I may not) Ecto will set the microsecond precision to 6 because thats what Postgres will return whereas the default NaiveDateTime will set the precision to 0.

If you use I think you’ll find they’ll be :eq meaning equal.


In Ecto master we will have naive_datetime and naive_datetime_usec, exactly to solve issues like this. Elixir v1.6 will also include a NaiveDateTime.truncate function, which makes it easier to set a given precision.


Thank you for feedback Kip, i used compare, but i was having issues in matching operations on my tests, at the point where i felt, there should be a better way to handle this :wink:

That’s great news José, thank you for the great work put on those projects, and the feedback of course :smile:


This might be related.

I noticed an oddity in the timestamps during insertion versus lookup:

My tests were failing in serialization of the naive_datetime. After I used the value from db lookup, tests ran fine.

> res = Repo.insert!(%Model{})
> res.inserted_at
~N[2018-01-10 13:25:52.122046]
> res_load = Repo.get!(
~N[2018-01-10 13:25:52.122000]

Not clear how it is possible for the actual insertion time to be later than reported by insert.

Stack: mongodb 3.4 / Ecto 2.1


It is possible that Mongo only has milliseconds precision and truncated the value.


Yes, unfortunately there is an issue at the moment with how the mongo ecto adapter handles the precision. It is something that is on my todo list.