Improve Performance with Streams

Streams

We know that the Stream data structure is lazily evaluated and allows us to process data only when needed. The Stream module has lazy implementations of map/2, filter/2, and other functions. We can use Stream.map/2 and Stream.filter/2 to replace their Enum counterparts, but what about reading and parsing the file?

Use File.stream!

Don’t worry, Elixir has us covered. The File module has a lazy equivalent to read!/1 called stream!/1, which is exactly what we need. The CSV module has parse_stream/1, which can replace parse_string/1. We have everything we need to convert our code from eager to lazy. Here’s the new version: