~petersanchez/migrate

#migrate

Database migrations for your Go project. Supports files, functions, and query migrations.

Version: 0.2.0

Project Links: Docs - Issues - Mailing List - Contributing

Author: Peter Sanchez (https://petersanchez.com)

#Requirements

Go 1.16+ (probably works with older, I just didn't test it)

#What?

This is a simple tool to manage database migrations from within your Go project. It's not a CLI tool, but a module that you plugin to your own project as needed.

It's based on github.com/joncalhoun/migrate but I've done many changes to make it fit my needs. That is why I am just maintaining my own fork versus submitting a PR. I feel mine has diverged too far from what Jon originally wanted.

Here's some of the changes:

Removed sqlx as dependency.
Added support for a global context.Context within migrations.
Added support for specific timeouts (via context.Context) per migration.
Added ability to specify a up (migrate) or down (rollback) specific version.
Added ability to "fake" a migration (up only). Essentially just adding the entry to migration history without actually running it. Useful for edge cases.
Added checks for migration ID duplication.
Added check to ensure migration ID exists when a specific ID is given. This is to avoid running migrations when an entry error has occurred.

My fork is a copy of the original repo as of this commit. I probably should have done a repo migration to Mercurial but here we are. All code up to the commit above is licensed under the MIT license, see the PREVIOUS_LICENSES document.

#Example usage

This example will assume you're using PostgreSQL as well (note the changing of binding type to migrate.DOLLAR).

Let's say you have a simple directory structure like so:

.
├── accounts
│   ├── input.go
│   ├── models.go
│   ├── routes.go
├── cmd
│   └── webapp
│       └── main.go
├── go.mod
├── go.sum
├── webapp_binary
├── Makefile
├── migrations
│   ├── 0001_initial_rollback.sql
│   └── 0001_initial.sql
├── templates
    ├── login.html
    └── register.html

You can see there is a migrations directory. You can store your migration files anywhere you want, but in this example we'll store them there.

Now let's add migrations to the main binary. We'll edit cmd/webapp/main.go to always call migrations when starting. I'm not recommending this, just a simple example.

import (
	...
	"petersanchez.com/migrate",
	...
)

func main() {
	// `db` is your database connection (*sql.DB)

	// Custom functions should be watching for the context's Done() channel
	migrations := []migrate.Migration{
		migrate.FileMigration("0001_initial", "migrations/0001_initial.sql", "migrations/0001_initial_rollback.sql", 0),
		migrate.Migration{
			ID: "0002_function",
			Migrate: func(ctx context.Context, tx *sql.Tx) error {
				// Run your migrate code here.
				return nil
			},
			Rollback: func(ctx context.Context, tx *sql.Tx) error {
				// Run your rollback code here.
				return nil
			},
			Timeout: 40, // Set a 40 second timeout on the functions
		},
	}

	if len(os.Args) > 0 {
		if os.Args[1] != "migrate" {
			err := migrate.Command(db, migrations, migrate.DOLLAR)
			// handle err
			os.Exit(0)
		}
	}

	// rest of your main() code
}

#Why?

I found the larger database migration projects for Go to be overkill for my needs. Especially if you wanted to run custom function migrations.

During my research I stumbled on an article titled Database migrations in Go by Jon Calhoun. I had already been thinking of how to create my own migrations package as minimally as possible and this article was close enough to what I was thinking. John even created the original migrate package, but it lacked several things I wanted in my migration solution.

So I stripped out external dependencies, added a bunch of stuff I wanted, and a few development hours later, here we are.

#Status

My needs are fairly simple and the current state of the module basically covers them. Please submit bugs and/or patches if you find any issues.

#Contributing

We accept patches submitted via hg email which is the patchbomb extension included with Mercurial.

The mailing list where you submit your patches is ~petersanchez/public-inbox@lists.code.netlandish.com. You can also view the archives on the web here:

https://lists.code.netlandish.com/~petersanchez/public-inbox

To quickly setup your clone of migrate to submit to the mailing list just edit your .hg/hgrc file and add the following:

[email]
to = ~petersanchez/public-inbox@lists.code.netlandish.com

[patchbomb]
flagtemplate = {separate(' ', 'migrate', flags)}

[diff]
git = 1

We have more information on the topic here:

#Copyright & Warranty

All documentation, libraries, and sample code are Copyright 2022 Peter Sanchez <pjs@petersanchez.com>. The library and sample code are made available to you under the terms of the BSD license which is contained in the included file, LICENSE.

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