Escape hatch for unsafe migrations

[guewen]

Hi!

Some migrations unfortunately cannot be run safely and are then impossible to run.
When using a partitioned table on PostgreSQL, this migration, where slots is the partitioned table, will fail because of 2 Postgres errors:

    add_reference :slots, :variation, index: true, foreign_key: true

1. ActiveRecord::StatementInvalid: PG::WrongObjectType: ERROR: cannot add NOT VALID foreign key on partitioned table "slots" referencing relation "variations": since validate: false is forced
2. PG::FeatureNotSupported: ERROR: cannot create index on partitioned table "stock_slots" concurrently : since algorithm: :concurrently is forced

Is there a way to explicitly disable the safeness in a block? If not, what about a block:

  unsafe_migration do
    add_reference :slots, :variation, index: true, foreign_key: true, validate: true
  end

Telling: I know it is not safe, and then it can be caught before deployment to take appropriate measures.

[guewen]

For the record, I found my way around using 3 distinct commands:

      add_column :slots, :variation_id, :integer
      add_foreign_key :slots, :variations, validate: true
      add_index :slots, :variation_id, algorithm: :default

[rchoquet]

Hey @guewen, thanks for taking the time to open this issue.

It's indeed not possible today.
I'd rather give a more explicit name to this method (ex: safe_pg_migrations_disable) like we already do for safe_pg_migrations_verbose.

Do you feel like giving a try at implementing it?