Models

Models is a SQL migration management tool. It supports PostgreSQL, MySQL, and SQLite.

Quick Start

install the CLI by running the following command:

$ cargo install models-cli

Now run the following command to create an environment file with the DATABASE_URL variable set:

$ echo "DATABASE_URL=sqlite://database.db" > .env

Alternatively it can be set as a environment variable with the following command:

$ export DATABASE_URL=sqlite://database.db

We now can create the database running the following command:

$ models database create

This command will have created an SQLite file called database.db. You can now derive the Model trait on your structures, and models will manage the migrations for you. For example, write at src/main.rs:

#![allow(dead_code)]
use models::Model;

#[derive(Model)]
struct Profile {
#[primary_key]
id: i32,
#[unique]
email: String,
password: String,
is_admin: bool,
}

#[derive(Model)]
struct Post {
#[primary_key]
id: i32,
#[foreign_key(Profile.id)]
author: String,
#[default("<Untitled Post>")]
title: String,
content: String,
}

#[derive(Model)]
struct PostLike {
#[foreign_key(Profile.id, on_delete="cascade")]
#[primary_key(post_id)]
profile_id: i32,
#[foreign_key(Post.id, on_delete="cascade")]
post_id: i32,
}

#[derive(Model)]
struct CommentLike {
#[foreign_key(Profile.id)]
#[primary_key(comment_id)]
profile_id: i32,
#[foreign_key(Comment.id)]
comment_id: i32,
is_dislike: bool,
}

#[derive(Model)]
struct Comment {
#[primary_key]
id: i32,
#[foreign_key(Profile.id)]
author: i32,
#[foreign_key(Post.id)]
post: i32,
}
fn main() {}

If you now run the following command, your migrations should be automatically created.

$ models generate

The output should look like this:

Generated: migrations/1632280793452 profile
Generated: migrations/1632280793459 post
Generated: migrations/1632280793465 postlike
Generated: migrations/1632280793471 comment
Generated: migrations/1632280793476 commentlike

You can check out the generated migrations at the migrations/ folder. To execute these migrations you can execute the following command:

models migrate run

The output should look like this:

Applied 1631716729974/migrate profile (342.208µs)
Applied 1631716729980/migrate post (255.958µs)
Applied 1631716729986/migrate comment (287.792µs)
Applied 1631716729993/migrate postlike (349.834µs)
Applied 1631716729998/migrate commentlike (374.625µs)

If we later modify those structures in our application, we can generate new migrations to update the tables.

Reverting migration

Models can generate down migrations with the -r flag. Note that simple and reversible migrations cannot be mixed:

$ models generate -r

In order to revert the last migration executed you can run:

$ models migrate revert

If you later want to see which migrations are yet to be applied you can also excecute:

$ models migrate info

Avaibale Attributes

primary_key

It's used to mark the primary key fo the table.

#[primary_key]
id: i32,

for tables with multicolumn primary keys, the following syntax is used:

#[primary_key(second_id)]
first_id: i32,
second_id: i32,

This is equivalent to:

PRIMARY KEY (first_id, second_id),

foreign_key

It is used to mark a foreign key constraint.

#[foreign_key(Profile.id)]
profile: i32,

It can also specify on_delete and on_update constraints:

#[foreign_key(Profile.id, on_delete="cascade")]
profile_id: i32,

This is equivalent to:

FOREIGN KEY (profile_id) REFERENCES profile (id) ON DELETE CASCADE,

default

It can be used to set a default value for a column.

#[default(false)] // when using SQLite use 0 or 1
is_admin: bool,
#[default("")]
text: String,
#[default(0)]
number: i32,

unique

It is used to mark a unique constraint.

#[unique]
email: String,

For multicolumn unique constraints the following syntax is used:

#[unique(post_id)]
profile_id: String,
post_id: i32,

This is equivalent to:

UNIQUE (profile_id, post_id),