For migrating between Redis databases on Heroku, when the source database doesn't support the sync Redis command

redis-migrate.rb

# For migrating between Redis databases on Heroku, when the source database doesn't support sync
# This is useful for migrating away from Redis Cloud, for example.
require "redis"

# You need to have created a new database first, with
# heroku addons:create heroku-redis:hobby-dev -a $APP
# OR
# heroku addons:create heroku-redis:premium-0 -a $APP


APP         = "YOUR_APP".freeze  # The Heroku app name
NEW_DB_NAME = "REDIS_URL".freeze # Change this if your new Redis database has a different name

SOURCE_DB = `heroku config:get REDISCLOUD_URL -a #{APP}`.chomp
DEST_DB   = `heroku config:get #{NEW_DB_NAME} -a #{APP}`.chomp

source = Redis.new(url: SOURCE_DB)
target = Redis.new(url: DEST_DB)

`heroku ps:scale worker=0 -a #{APP}`
`heroku maintenance:on -a #{APP}`

source.keys("*").each do |key|
  data = source.dump key
  # puts key, data
  target.restore key, 0, data
end

# You might need to change this to be appropriate for you
`heroku config:set REDIS_PROVIDER=#{NEW_DB_NAME} -a #{APP}`
`heroku maintenance:off -a #{APP}`
`heroku ps:scale worker=1 -a #{APP}`

Sounds like your source and target databases might be different versions. If that's the case, I'd suggest separating the migration and the version upgrade into two different steps.

Interesting idea. Thank you ;)