Ecto/MySQL/Binary id bug

as sugested by https://elixirforum.com/t/odd-binary-id-mismatch/14719/11 created this seperate project for this bug to be isolated and easier to replicate.

Bug description

After inserting row in mysql table it seems to have different id in mysql table, but i can receive inserted row by both ids.

Problems:

why id is changed while inserting in mysql table, and why it isnt changed for struct returned from Repo.insert!
why i can retrieve the same row with 2 different ids?

Beginings

Usage

clone
update mysql connection params in config/config.exs
mix ecto.create
mix ecto.migrate
mix test

Actual Environment to replicate the problem

elixir environment	mysql environment	can reproduce bug
Mac OS 10.13.5 (17F77)	Mac OS 10.13.5 (17F77)	No
Mac OS 10.13.5 (17F77)	Ubuntu 16.04.4 LTS	Yes
Ubuntu 16.04.4 LTS	Ubuntu 16.04.4 LTS	Yes

Elixir version (elixir -v):

Erlang/OTP 21 [erts-10.0] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [hipe]

Elixir 1.6.6 (compiled with OTP 20)

Database and version (PostgreSQL 9.4, MongoDB 3.2, etc.):

MySQL 5.7.22 and 8.0.11

Ecto version (mix deps):

ecto 2.2.10 (Hex package) (mix) locked at 2.2.10 (ecto) e7366dc8

Database adapter and version (mix deps):

mariaex 0.8.4 (Hex package) (mix) locked at 0.8.4 (mariaex) 5dd42a60

Operating system:

Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-101-generic x86_64) Codename: xenial

Error inconsistencies

Most of the time test fails with

  1) test With autogenerated id (Bug.BugTest)
     test/bug_test.exs:7
     Assertion with == failed
     code:  assert new.id() == entity.id()
     left:  "745f3f31-043f-433f-3f7e-3f4e3f293c3f"
     right: "745f8031-04c7-43b4-b67e-9d4ec1293ca9"
     stacktrace:
       test/bug_test.exs:14: (test)



  2) test With pregenerated id (Bug.BugTest)
     test/bug_test.exs:17
     Assertion with == failed
     code:  assert new.id() == entity.id()
     left:  "6f3f2c73-183f-4345-3f3f-3f353f3f3a3f"
     right: "6f9b2c73-18be-4345-90ad-993589ac3aa8"
     stacktrace:
       test/bug_test.exs:26: (test)

Sometimes it sortof works:

  1) test With autogenerated id (Bug.BugTest)
     test/bug_test.exs:7
     ** (Ecto.NoResultsError) expected at least one result but got none in query:

     from p in Bug.PrimaryModule,
       where: p.id == ^"063fdf04-d61d-4b14-a66e-0493d52cdbdd"

     code: new = Repo.get!(PrimaryModule, entity.id)
     stacktrace:
       (ecto) lib/ecto/repo/queryable.ex:80: Ecto.Repo.Queryable.one!/4
       test/bug_test.exs:10: (test)