动态子类化和ActiveRecord与PostgreSQL数据库建立连接

I'm trying to create a utility to copy a subset of records from a single table of one PostgreSQL database to that same table in another PostgreSQL database. I'm doing this with dynamic subclassing, but it's not working: it raises the error "xxx database is not configured" (where xxx is my database URL, something like "postgres://username:password@computername:5432/databasename". I know the URL is good because I copied it from my Heroku configuration and I am able to access the database from pgAdmin3 on my local machine. Here's the code:I'm trying to create a utility to copy a subset