ecto-migrator

# Ecto Migrator

## Generating Migrations

### From Natural Language

Parse the user's description and generate a migration file. Common patterns:

| User Says | Migration Action |
|-----------|-----------------|
| "Create users table with email and name" | `create table(:users)` with columns |
| "Add phone to users" | `alter table(:users), add :phone` |
| "Make email unique on users" | `create unique_index(:users, [:email])` |
| "Add tenant_id to all tables" | Multiple `alter table` with index |
| "Rename status to state on orders" | `rename table(:orders), :status, to: :state` |
| "Remove the legacy_id column from users" | `alter table(:users), remove :legacy_id` |
| "Add a check constraint on orders amount > 0" | `create constraint(:orders, ...)` |

### File Naming

```bash
mix ecto.gen.migration <name>
# Generates: priv/repo/migrations/YYYYMMDDHHMMSS_<name>.exs
```

Name conventions: `create_<table>`, `add_<column>_to_<table>`, `create_<table>_<column>_index`, `alter_<table>_add_<columns>`.

## Migration Template

```elixir
defmodule MyApp.Repo.Migrations.CreateUsers do
  use Ecto.Migration

  def change do
    create table(:users, primary_key: false) do
      add :id, :binary_id, primary_key: true
      add :email, :string, null: false
      add :name, :string, null: false
      add :role, :string, null: false, default: "member"
      add :metadata, :map, default: %{}
      add :tenant_id, :binary_id, null: false

      add :team_id, references(:teams, type: :binary_id, on_delete: :delete_all)

      timestamps(type: :utc_datetime_usec)
    end

    create unique_index(:users, [:tenant_id, :email])
    create index(:users, [:tenant_id])
    create index(:users, [:team_id])
  end
end
```

## Column Types

See [references/column-types.md](references/column-types.md) for complete type mapping and guidance.

Key decisions:
- **IDs**: Use `:binary_id` (UUID) — set `primary_key: false` on table, add `:id` manually.
- **Money**: Use `:integer` (cents) or `:decimal` —...