Superfast CSV imports using PostgreSQL's COPY command

Dealing with various sources of data in web applications requires us to create services that will extract information from CSV, Excel, and other file types. In that case, it's best to use some existing libraries, or if your backend is on Rails, use gems. There are many gems with very cool features like CSVImporter and Roo. But you can also use plain Ruby CSV.Either way, if those are small CSV files, you will get your job done easily. But what if you need to import large CSV files (~100MB / ~1M rows)?.