Represents an SQL table in an abstract way for updating a table. Also see TableDefinition and ActiveRecord::ConnectionAdapters::SchemaStatements#create_table
Available transformations are:
change_table :table do |t| t.column t.index t.timestamps t.change t.change_default t.rename t.references t.belongs_to t.string t.text t.integer t.float t.decimal t.datetime t.timestamp t.time t.date t.binary t.boolean t.remove t.remove_references t.remove_belongs_to t.remove_index t.remove_timestamps end
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Changes the column’s definition according to the new options. See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.
Examples
t.change(:name, :string, :limit => 80) t.change(:description, :text)
Sets a new default value for a column. See ActiveRecord::ConnectionAdapters::SchemaStatements#change_column_default
Examples
t.change_default(:qualification, 'new') t.change_default(:authorized, 1)
Adds a new column to the named table. See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.
Example
Creating a simple column
t.column(:name, :string)
Checks to see if a column exists. See ActiveRecord::ConnectionAdapters::SchemaStatements#column_exists?
Adds a new index to the table. column_name
can be a single Symbol, or an Array of Symbols. See ActiveRecord::ConnectionAdapters::SchemaStatements#add_index
Examples
Creating a simple index
t.index(:name)
Creating a unique index
t.index([:branch_id, :party_id], :unique => true)
Creating a named index
t.index([:branch_id, :party_id], :unique => true, :name => 'by_branch_party')
Checks to see if an index exists. See ActiveRecord::ConnectionAdapters::SchemaStatements#index_exists?
Adds a reference. Optionally adds a type
column, if
:polymorphic
option is provided. references
and
belongs_to
are acceptable.
Examples
t.references(:goat) t.references(:goat, :polymorphic => true) t.belongs_to(:goat)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 432 def references(*args) options = args.extract_options! polymorphic = options.delete(:polymorphic) args.each do |col| @base.add_column(@table_name, "#{col}_id", :integer, options) @base.add_column(@table_name, "#{col}_type", :string, polymorphic.is_a?(Hash) ? polymorphic : options) unless polymorphic.nil? end end
Removes the column(s) from the table definition.
Examples
t.remove(:qualification) t.remove(:qualification, :experience)
Removes the given index from the table.
Examples
Remove the index_table_name_on_column in the table_name table
t.remove_index :column
Remove the index named index_table_name_on_branch_id in the table_name table
t.remove_index :column => :branch_id
Remove the index named index_table_name_on_branch_id_and_party_id in the table_name table
t.remove_index :column => [:branch_id, :party_id]
Remove the index named by_branch_party in the table_name table
t.remove_index :name => :by_branch_party
Removes a reference. Optionally removes a type
column.
remove_references
and remove_belongs_to
are
acceptable.
Examples
t.remove_references(:goat) t.remove_references(:goat, :polymorphic => true) t.remove_belongs_to(:goat)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 448 def remove_references(*args) options = args.extract_options! polymorphic = options.delete(:polymorphic) args.each do |col| @base.remove_column(@table_name, "#{col}_id") @base.remove_column(@table_name, "#{col}_type") unless polymorphic.nil? end end
Removes the timestamp columns (created_at
and
updated_at
) from the table.
Example
t.remove_timestamps
Renames a column.
Example
t.rename(:description, :name)
Adds timestamps (created_at
and updated_at
)
columns to the table. See ActiveRecord::ConnectionAdapters::SchemaStatements#add_timestamps
Example
t.timestamps