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Version: 0.4

Migration operations

This page provides a reference for all the available migration operations that can be leveraged when writing migrations.

add_column​

The add_column operation allows adding a column to an existing table. It must be called with a table name as first argument, followed by a column definition (column name and attributes).

For example:

add_column :test_table, :foo, :string, max_size: 255
add_column :test_table, :new_id, :reference, to_table: :target_table, to_column: :id

add_index​

The add_index operation allows adding an index to an existing table. It must be called with a table name as first argument, followed by an index definition (index name and indexed column names).

For example:

add_index :test_table, :test_index, [:foo, :bar]

add_unique_constraint​

The add_unique_constraint operation allows adding a unique constraint to an existing table. It must be called with a table name as first argument, followed by a unique constraint definition (constraint name and targetted column names).

For example:

add_unique_constraint :test_table, :test_constraint, [:foo, :bar]

change_column​

The change_column operation allows altering an existing column definition. It must be called with a table name as first argument, followed by a column definition (column name and attributes).

For example:

change_column :test_table, :test_column, :string, max_size: 155, null: true

create_table​

The create_table operation allows creating a new table, which includes the underlying column definitions, indexes, and unique constraints. It must be called with a table name as first argument and requires a block where columns, indexes, and unique constraints are defined.

For example:

create_table :test_table do
  column :id, :big_int, primary_key: true, auto: true
  column :foo, :int, null: true
  column :bar, :int, null: true

  unique_constraint :cname, [:foo, :bar]
  index :index_name, [:foo, :bar]
end

delete_table​

The delete_table operation allows deleting an existing table. It must be called with a table name as first argument.

For example:

delete_table :test_table

execute​

The execute operation allows executing custom SQL statements as part of a migration. It must be called with a forward statement as first positional argument, and it can also take a second positional argument in order to specify the statement to execute when unapplying the migration.

For example:

execute(
  (
    <<-SQL
    SELECT 1
    SQL
  ),
  (
    <<-SQL
    SELECT 2
    SQL
  )
)

remove_column​

The remove_column operation allows removing an existing column from a table. It must be called with a table name as first argument, followed by a column name.

For example:

remove_column :test_table, :test_column

remove_index​

The remove_index operation allows removing an existing index from a table. It must be called with a table name as first argument, followed by an index name.

For example:

remove_index :test_table, :test_index

remove_unique_constraint​

The remove_unique_constraint operation allows removing an existing unique constraint from a table. It must be called with a table name as first argument, followed by a unique constraint name.

For example:

remove_unique_constraint :test_table, :test_constraint

rename_column​

The rename_column operation allows renaming an existing column in a table. It must be called with a table name as first argument, followed by the old column name, and the new one.

For example:

rename_column :test_table, :old_column, :new_column

rename_table​

The rename_table operation allows renaming an existing table. It must be called with the existing table name as first argument, followed by the new table name.

For example:

rename_table :old_table, :new_table

run_code​

The run_code operation allows to define that arbitrary methods will be called when applying and unapplying a migration. It must be called with a method name as first positional argument (the method that will be called when applying the migration), and it can also take an additional argument in order to specify the name of the method to execute when unapplying the migration.

For example:

run_code :run_forward_code, :run_backward_code