Managing Data
Data is an integral part of virtually any web application, and a great persistence library make a huge difference in performance and maintainability.
Thankfully, the Elixir ecosystem has us covered in spades. Ecto is a thin layer of functions that allow us to build composable queries, validate fields, and seamlessly transform records between our DB and application representations.
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Managing DataIntro to Ecto
Heavy persistence libraries like ActiveRecord offer convenience, but often become performance bottlenecks. We could make every DB query explicitly, but then we're trading in all of our ergonomics for performance.
Ecto manages to strike an enjoyable balance, where we are asked to be deliberate about the records we fetch from a database but (most of the time) aren't dragged into the world of writing SQL queries explicitly.
You'll be amazed at how much we can do with just simple functions, and will never look at other persistence frameworks quite the same way again.
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Managing DataSchema & Managing Migrations
If you've never used code to manage changes to your database schema, you're missing out. Migrations allow us to change our schema in (ideally) reversible steps, so we can apply and un-apply a set of changes while building features.
Even if you've seen migrations before, there are some useful things to know about how they work with Ecto, and in particular, Postgres. We'll look specifically at:
- Postgres array and jsonb column types
- Changing column types, while remaining backwards compatible
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Managing DataEXERCISE: Ecto Models
Make Ecto models to match the provided specifications (and successive changes to specifications). Ensure all of your DB migrations are reversible, and backwards compatible.
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Managing DataCracking Changesets
This is one of my favorite parts about Ecto, and one of the parts you'll be most often working with. In contrast to other persistence libraries, the concept of the shape of a record (schema) and the logic for checking the validity of values (validations) are decoupled. There are some incredibly exciting consequences of this design decision.
Ecto ships with a bunch of validations, and because it's so quick and easy, we'll write a few of our own.
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Managing DataEXERCISE: Validating for Password Complexity
Create a new field on our User model that validates the password field, ensuring that:
- it's not empty
- it has a minimum length of 8 characters
- it includes an upper-case letter, symbol, lower case letter, and a number
- it doesn't include more than two successive letters or numbers like
abcor123
Failing any of this validation should be met with an appropriately descriptive error message.
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Managing DataRecap & Wrap Up
We'll recap the topics we've covered today, answer any remaining questions, and preview the topics we'll cover tomorrow.