neiam /apollos_crib

It's Apollo's Crib

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Renumber a migration that collided, and catch the next one

51830b0 · Gabriel Morell · 2026-09-05 20:40

9 files +49 -0

Message

{commit_body(@commit)}

Files changed

renamed apps/room_sanctum/priv/repo/migrations/20260905120000_add_tint_to_foci.exs → apps/room_sanctum/priv/repo/migrations/20260905122000_add_tint_to_foci.exs

+5 −0

@@ -10,6 +10,11 @@ defmodule RoomSanctum.Repo.Migrations.AddTintToFoci do

10	10	a tint of foci gains a new one the moment it is tinted.
11	11	"""
12	12
	13	+ # Renumbered from 20260905120000, which collided with add_plus_to_pythiae.
	14	+ # Ecto keys schema_migrations on the version alone, so the first of the two
	15	+ # to run recorded the number and the second was skipped -- while still
	16	+ # reporting `:up`, because the version it is looked up by was there.
	17	+ # Silent, and it looked exactly like a migration that had run.
13	18	def change do
14	19	alter table(:cfg_focis) do
15	20	add :tint, :string

added apps/room_sanctum/test/room_sanctum/migrations_test.exs

+44 −0

@@ -0,0 +1,44 @@

	1	+defmodule RoomSanctum.MigrationsTest do
	2	+ use ExUnit.Case, async: true
	3	+
	4	+ @migrations Path.join([__DIR__, "..", "..", "priv", "repo", "migrations"])
	5	+
	6	+ # What Ecto itself considers a migration: a leading version, then a name.
	7	+ # The directory also holds a .formatter.exs, which is not one.
	8	+ defp migration_files do
	9	+ @migrations
	10	+ \|> File.ls!()
	11	+ \|> Enum.filter(&Regex.match?(~r/^\d+_.*\.exs$/, &1))
	12	+ end
	13	+
	14	+ test "no two migrations share a version" do
	15	+ # Ecto keys schema_migrations on the version alone. Two files with the
	16	+ # same number means the first to run records it and the second is skipped
	17	+ # -- and then reports itself up, because the version it is looked up by
	18	+ # is there. Nothing errors, nothing logs, and the column simply does not
	19	+ # exist. That cost an afternoon of a Plani crash-looping in production
	20	+ # against a table it had been told was migrated.
	21	+ duplicates =
	22	+ migration_files()
	23	+ \|> Enum.group_by(fn file -> file \|> String.split("_") \|> hd() end)
	24	+ \|> Enum.filter(fn {_version, files} -> length(files) > 1 end)
	25	+
	26	+ assert duplicates == [],
	27	+ "these migrations share a version, and all but one will be skipped:\n" <>
	28	+ Enum.map_join(duplicates, "\n", fn {version, files} ->
	29	+ " #{version}: #{Enum.join(files, ", ")}"
	30	+ end)
	31	+ end
	32	+
	33	+ test "every migration is named after a version that sorts" do
	34	+ # Ecto runs them in version order, so a name it cannot parse a number out
	35	+ # of would run somewhere unpredictable.
	36	+ for file <- migration_files() do
	37	+ assert {version, "_" <> _rest} = Integer.parse(file)
	38	+ assert version > 0, "#{file} has no leading version"
	39	+ end
	40	+
	41	+ # And that the filter is not vacuously true.
	42	+ assert length(migration_files()) > 10
	43	+ end
	44	+end

Parents: b0906f0