Changesets are an advanced abstraction for making changes in your database. They work on top of commands, and provide additional data mapping functionality and have support for associating data.
Built-in changesets support all core command types, you can also define custom changeset classes and connect them to custom commands.
Working with changesets
You can get a changeset object via Relation#changeset interface. A changeset object wraps input data, and may optionally convert it into a representation that's compatible with your database schema.
Assuming you have a users relation available:
:create
users.changeset(:create, name: "Jane").commit
=> {:id=>1, :name=>"Jane"}
:update
users.by_pk(4).changeset(:update, name: "Jane Doe").commit
=> {:id=>4, :name=>"Jane Doe"}
Warning
Update changesets check the difference between the original tuple and new data. If there's no diff, an update changeset will not execute its command.
:delete
users.by_pk(4).changeset(:delete).commit
=> {:id=>4, :name=>"Jane Doe"}
users.by_pk(4).changeset(:delete).commit
# => nil
Note
In the examples above, we used Relation#by_pk method, this is a built-in method which restricts a relation by its primary key; however, you can use any method that's available, including native adapter query methods.