https://github.com/hkalexling/mg

A minimal database migration tool for Crystal
https://github.com/hkalexling/mg

crystal database migration-tool

Last synced: 21 days ago
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A minimal database migration tool for Crystal

• Host: GitHub
• URL: https://github.com/hkalexling/mg
• Owner: hkalexling
• License: mit
• Created: 2021-01-16T14:14:10.000Z (almost 4 years ago)
• Default Branch: master
• Last Pushed: 2021-07-11T01:28:33.000Z (over 3 years ago)
• Last Synced: 2024-05-23T01:06:10.215Z (6 months ago)
• Topics: crystal, database, migration-tool
• Language: Crystal
• Homepage: https://hkalexling.github.io/mg/
• Size: 77.1 KB
• Stars: 8
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# MG

A minimal database migration tool for Crystal.

## Installation

1. Add the dependency to your `shard.yml`:

```yaml

dependencies:

 mg:

   github: hkalexling/mg

```

2. Run `shards install`

## Usage

First define some database versions by inheriting from `MG::Base`. Here are two examples:

```crystal

# migration/users.1.cr

class CreateUser < MG::Base

  def up : String

    <<-SQL

    CREATE TABLE users (

     username TEXT NOT NULL,

     password TEXT NOT NULL,

     email TEXT NOT NULL

    );

    SQL

  end

  def down : String

    <<-SQL

    DROP TABLE users;

    SQL

  end

  # Optional lifecycle method to be executed after the `up` query.

  def after_up(conn : DB::Connection)

    puts "Table users created"

  end

  # Optional lifecycle method to be executed after the `down` query.

  def after_down(conn : DB::Connection)

    puts "Table users dropped"

  end

end

```

```crystal

# migration/users_index.2.cr

class UserIndex < MG::Base

  def up : String

    <<-SQL

    CREATE UNIQUE INDEX username_idx ON users (username);

    CREATE UNIQUE INDEX email_idx ON users (email);

    SQL

  end

  def down : String

    <<-SQL

    DROP INDEX username_idx;

    DROP INDEX email_idx;

    SQL

  end

end

```

Note that the migration files must be named as `[filename].[non-negative-version-number].cr`.

Now require the relevant files and the migrations in your application code, and start the migration.

```crystal

require "mg"

require "sqlite3"

require "./migration/*"

Log.setup "mg", :debug

DB.open "sqlite3://file.db" do |db|

  mg = MG::Migration.new db

  # Migrates to the latest version (in our case, 2)

  mg.migrate

  # Migrates to a specific version

  mg.migrate to: 1

  # Migrates down to version 0

  mg.migrate to: 0

  # Returns the current version

  puts mg.user_version # 0

end

```

## Contributors

- [Alex Ling](https://github.com/hkalexling) - creator and maintainer