Database migrations and versioning

Each engine of Lesli has it's own migration prefix which conforms the first 4 digits of the migration file.

Explaning migrations code

The migration code is conformed by engine code + migration identifier + version

Engine Code: 0100 (CCEE)

Migration identifier: 0001 (NNTT)

Folder Version: v10 (VV)

Code: 0100000110 (CCEENNTTVV)

Database versioning

Every stable version of the platform should come with their own database structure; Lesli database version is completely different from Rails migration versioning.

Every change (version) of the database should be in their own folder, the folder should be named with the name of the current working version of the system and the migration should be sufixed with the same version that we are currently working on.

Database versioning example

version	migration name
version 1.0	0100000310_create_test (base migration)
version 1.1	0100000311_alter_test (add a new field)
version 1.2	0100000312_alter_test (add a new field)
version 2.0	0100000320_alter_test (change field from string to integer)

Database versioning standard

Create Table

The correct migration name to create a table is create_table_name.

Example:

Assuming we have the following migrations defined and we want to create new table (user_shortcuts).

v1.0/
    01000000310_create_users.rb
    01000003110_create_user_details.rb
    01000003210_create_user_settings.rb
    01000003310_create_user_sessions.rb
    01000003410_create_user_requests.rb
    01000003510_create_user_activites.rb
    01000003610_create_user_roles.rb
    01000003710_create_user_logs.rb
    01000003810_create_user_access_codes.rb

The correct migration code is 0100003811.

Explanation:
- Engine code: 0100
- Migration identifier prefix for users: 003
- Available identifier sufix for users: 9
- Folder version: 1.1

1. Create migration using the scaffold generator

  rails generate scaffold user_shortcuts

3. Rename the migration with a standard name.

  20211029165345_create_user_shortcuts.rb ——> /v1.1/01000003911_create_user_shortcuts.rb

Alter Table

For any change on the table the correct migration name is alter_table_name.

• Add column
• Rename column
• Remove column
• Change column type

Example:

Assuming we have the following database definition.

class CreateTests < ActiveRecord::Migration[6.0]
    def change
        create_table :tests do |t|
            t.string    :name
            t.string    :description
            t.boolean   :active

            t.timestamps
        end
    end
end

1. Add a new field on the table.

  rails generate migration alter_tests

2. Rename the migration with a standard name.

  20211029165321_alter_tests.rb ——> /v1.1/0100000111_alter_tests.rb

3. Add a new column.

class CreateTests < ActiveRecord::Migration[6.0]
    def change
        add_column :tests, :importance, :string
    end
end

Drop Table

The correct migration name to delete a table is drop_table_name.

Example:
1. Create migration

  rails generate migration drop_tests

2. Rename the migration with a standard name

  20211029165321_drop_tests.rb ——> /v1.2/0100000112_drop_tests.rb

3. Drop table

class DropTests < ActiveRecord::Migration[6.1]
    def change
        drop_table :tests
    end
end