class Clear::Migration::Manager


The migration manager is a singleton, it load all the migrations, check which one are #up and #down, and can trigger one or multiple downgrade / upgrade of the database.

The migration system needs the creation of a table named __clear_metadatas in your database. This table will be created automatically on the first initialization of the Migration Manager.

Included Modules

Defined in:


Constant Summary


Used to migrate between metadata version, in case we need it in the future.

Class Method Summary

Instance Method Summary

Instance methods inherited from module Clear::ErrorMessages

build_error_message(message : String, ways_to_resolve : Tuple | Array =, manual_pages : Tuple | Array = build_error_message, converter_error(from, to) converter_error, format_width(x, w = 80) format_width, illegal_setter_access_to_undefined_column(name) illegal_setter_access_to_undefined_column, lack_of_primary_key(model_name) lack_of_primary_key, migration_already_down(number) migration_already_down, migration_already_up(number) migration_already_up, migration_drop_irreversible(name) migration_drop_irreversible, migration_irreversible(name = nil, operation = nil) migration_irreversible, migration_not_found(number) migration_not_found, migration_not_unique(numbers) migration_not_unique, no_migration_yet(version) no_migration_yet, null_column_mapping_error(name, type) null_column_mapping_error, order_by_error_invalid_order(current_order) order_by_error_invalid_order, polymorphic_nil(through) polymorphic_nil, polymorphic_unknown_class(class_name) polymorphic_unknown_class, query_building_error(message) query_building_error, uid_not_found(class_name) uid_not_found, uninitialized_db_connection(connection) uninitialized_db_connection

Class Method Detail

def self.instance #

To access to the manager


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Instance Method Detail

def apply_all #

Apply all the migrations not yet applied.

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def apply_to(version, direction = :both) #

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def commited?(m : Clear::Migration) #

Return true if the migration has been commited (already applied into the database) or false otherwise

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def current_version #

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def down(number : Int64) : Nil #

Force down a migration; throw error if the mgiration is already down

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def ensure_ready #

Create if needed the metadata table to save the migrations.

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def find(number) #

Fetch the migration instance with the selected number

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def load_existing_migrations #

Fetch all the migrations already activated on the database.

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def max_version #

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def migrations_up #

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def print_status : String #

Print out the status ( up | down ) of all migrations found by the manager.

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def refresh #

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def reinit! #

Force reloading the migration system Recheck all the current up migrations and the metadata table. This is useful if you access to the migration process through another program, or during specs

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def up(number : Int64) : Nil #

Force up a migration; throw error if the migration is already up

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