Crate sql_from_models

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 sql_from_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:

$ sql_from_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 sql_from_models will manage the migrations for you. For example, write at src/main.rs:

#![allow(dead_code)]
use sql_from_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.

$ sql_from_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:

sql_from_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:

$ sql_from_models generate -r

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

$ sql_from_models migrate revert

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

$ sql_from_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),

Re-exports

• pub use types::*;

Modules

• error
• private
  This module is publicly accessible, but the interface can be subject to changes. This module is intended for macros only. Changes to elements in this module are not considered a breaking change. Do not depend directly on this module.
• types
  Types

Derive Macros

• Model