Squill

Squill manages Postgresql database migrations.

There's no shortage of tools for running migrations, but this one embodies my particular opinions:

  1. Migrations should be written in database-specific SQL.
  2. Migrations are not generally idempotent or reversible in production, but reversals (down migrations) are very useful during development.
  3. Migration dependencies form a tree structure, not a linear sequence.

What's a squill?

It's the common name for a subfamily of plants that are actually pretty cool looking.

But more importantly, it's a word that has the letters "s", "q", and "l" in that order, is easy to type and pronounce, and not already someone else's crate name 😉

Installation

To install Squill as a command, use cargo install:

bash cargo install squill

To use Squill as a library, add this to your Cargo.toml:

bash squill = "0.4.2"

Usage

Run squill --help to get usage information from each subcommand.

First-time setup

Write the configuration file (squill.toml) or set the equivalent environment variables. The environment variables take precedence over the file.

The environment variables are uppercase versions of the ones in the file with SQUILL_ prefixes. For example, database_url is SQUILL_DATABASE_URL.

```toml

The connection string for the database to run migrations on.

#

You might prefer to set this using an environment variable.

#

Default: "" (default PostgreSQL server)

database_url = ""

The directory used to store migration files.

#

Default: "migrations"

migrations_dir = "migrations"

The template to use for new migration files.

#

Default: (unset) (use the embedded default migration templates)

templates_dir = ".squill/templates" ```

Then, generate the first migration that sets up Squill's requirements:

bash squill init

That should have written 0-init/{up,down}.sql to your migrations directory. Read through those files and make any changes you want.

Finally, run the up migration:

bash squill migrate

Writing a new migration

Create a new empty migration file:

bash squill new --name 'create_users_table'

(You can override the automatic ID generation with --id 123).

Write your migration in the file. Then run it:

bash squill migrate

Undoing a migration

For a migration that has already been run in production (or some other shared environment), the best option is to write a new migration to undo the old one.

In a development environment, undo the most recently run migration (by application order, not by ID):

bash squill undo

Edit the up migration, and then use squill migrate as normal to run it.

To make this easier, squill redo will run down.sql and then up.sql for the most recently run migration.

Renumbering migrations

You may have a mix of migrations with different ID lengths, which can make it awkward to sort the directories. Use the renumber subcommand to zero-pad shorter IDs:

bash squill renumber

That command is just a preview by default. Add --write to actually execute the renaming.

Custom migration templates

You can customize the files generated by squill new by setting the templates_dir path. Squill will use the new.up.sql and new.down.sql files in that directory as [Tera] templates to generate the respective up and down migration files.

The Tera context will be something like this: id: &i64 name: &str

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Join me!

I welcome contributions from anyone who finds a way to make this better.

In particular, I appreciate these things: - Pull requests with clear motivation (tests are nice too!) - Bug reports with reproducible setup instructions - Ideas about things that work but can be improved - Comments in issues and PRs to help me write better words and code

Support

This is is hobby project, so I'll only work on it as much as I find it fun to do so. That said, I find software maintenance techniques interesting, so feel free to start a conversation about a stable v1 if you start relying on this for something important.