Rollback Migrations

This guide shows you how to rollback database migrations.

Rollback Last Migration

migrator = MyDB.migrator(config)
migrator.down
puts "Rolled back one migration"

Rollback Multiple Migrations

# Rollback last 3 migrations
3.times { migrator.down }

Rollback to Specific Version

# Rollback to version 5
migrator.down_to(5)

Rollback All Migrations

# Rollback everything (use with caution!)
migrator.down_to(0)

Check Before Rollback

puts "Current version: #{migrator.current_version}"
puts "Applied migrations: #{migrator.applied_migrations.size}"

# Only rollback if there are migrations to rollback
if migrator.applied_migrations.any?
  migrator.down
  puts "Rolled back to version: #{migrator.current_version}"
else
  puts "No migrations to rollback"
end

Safe Rollback Script

# src/rollback.cr
require "./database"
require "../migrations/*"

MyDB.init

config = CQL::MigratorConfig.new(
  schema_file_path: "src/schemas/app_schema.cr",
  schema_name: :AppSchema,
  auto_sync: true
)

migrator = MyDB.migrator(config)

current = migrator.current_version
puts "Current version: #{current}"

if current == 0
  puts "No migrations to rollback"
  exit 0
end

print "Rollback migration #{current}? (y/n): "
if gets.try(&.strip) == "y"
  migrator.down
  puts "Rolled back to version: #{migrator.current_version}"
else
  puts "Cancelled"
end

Handle Irreversible Migrations

Some migrations can't be rolled back:

class DropLegacyTable < CQL::Migration(10)
  def up
    schema.legacy_users.drop!
  end

  def down
    # Can't restore dropped table with data
    raise "Cannot rollback: table was dropped with data"
  end
end

When you try to rollback:

begin
  migrator.down
rescue ex
  puts "Rollback failed: #{ex.message}"
end

Refresh Database

Rollback all and re-migrate (development only):

def refresh_database
  migrator = MyDB.migrator(config)

  puts "Rolling back all migrations..."
  migrator.down_to(0)

  puts "Re-running all migrations..."
  migrator.up

  puts "Database refreshed"
end

Verify Rollback

migrator = MyDB.migrator(config)

# Record current state
before = migrator.applied_migrations.size

# Rollback
migrator.down

# Verify
after = migrator.applied_migrations.size
puts "Rolled back: #{before} -> #{after} migrations"

Related

• Create a Migration

• Run Migrations

• Migration DSL Reference