Changesets

Let's now analyze how can we update the information stored in the database. The way Ecto allows you to change this information may feel weird at first, since it asks you to always use a changeset that describes how the data manipulation should be accomplished. These changesets will help us to ensure the changes we are persisting are valid and don't break any of the constraints we have in place.

To understand how changesets can be helpful, let's imagine the following scenario, using an object-oriented language with an Object-Relational Mapping framework: you have a media object with dozens of fields, and you update a couple of them, then you perform a media.save and those two fields will be updated on the database row for that particular media. To compose the actual SQL update statement, the ORM needs to know how to identify the fields that changed, and issue the update statement only for those. The ORM will also do some validations for you and halt the execution of the SQL statement...