ecto-migration - SKILL.md Agent Skill

name: ecto-migration description: Generates Ecto migrations for the Blockscout Elixir project using mix ecto.gen.migration command. Use when you need to create database schema changes, add tables, modify columns, or manage database structure.

Overview

The ecto-migration skill generates new Ecto migration files for the Blockscout project using the Mix task. Migrations are used to evolve the database schema over time in a versioned and controlled manner.

When to Use

When creating new database tables
When modifying existing table structures (add/remove/change columns)
When adding or removing database indexes
When performing data migrations or transformations
When implementing database constraints or relationships

How to Apply

Run the following command from the workspace root:

mix ecto.gen.migration [migration_name] -r Explorer.Repo

Replace [migration_name] with a descriptive name for your migration using snake_case (e.g., add_users_table, alter_transactions_status).

What It Does

Creates a new migration file in apps/explorer/priv/repo/migrations/ directory
Generates a timestamped filename to ensure proper ordering
Provides a basic migration template with change/0 or up/0 and down/0 functions
Targets the Explorer.Repo repository specifically

Example Usage

Generate a migration to add a new column:

mix ecto.gen.migration add_metadata_to_blocks -r Explorer.Repo

This creates a file like:

apps/explorer/priv/repo/migrations/20260220123456_add_metadata_to_blocks.exs

Then edit the generated file to implement your schema changes:

defmodule Explorer.Repo.Migrations.AddMetadataToBlocks do
  use Ecto.Migration

  def change do
    alter table(:blocks) do
      add :metadata, :jsonb
    end
  end
end

Notes

Always use descriptive migration names
The -r Explorer.Repo flag specifies the repository (required for umbrella apps)
Migration files are timestamped automatically to maintain order
After creating a migration, edit it to implement the actual schema changes
Run mix ecto.migrate to apply the migration to your database
Use mix ecto.rollback to revert the last migration if needed
For complex operations, consider using up/0 and down/0 instead of change/0