Schema::AlterTableGenerator is an internal class that the user is not expected to instantiate directly. Instances are created by Sequel::Database#alter_table. It is used to specify table alteration parameters. It takes a Database object and a block of operations to perform on the table, and gives the Database an array of table altering operations, which the database uses to alter a table's description.
For more information on Sequel's support for schema modification, see the "Schema Modification" guide.
An array of DDL operations to perform
Set the Database object to which to apply the DDL, and evaluate the block in the context of this object.
# File lib/sequel/database/schema_generator.rb, line 288 def initialize(db, &block) @db = db @operations = [] instance_eval(&block) if block end
Add a column with the given name, type, and opts to the DDL for the table. See Sequel::Schema::CreateTableGenerator#column for the available options.
add_column(:name, String) # ADD COLUMN name varchar(255)
# File lib/sequel/database/schema_generator.rb, line 298 def add_column(name, type, opts = {}) @operations << {:op => :add_column, :name => name, :type => type}.merge(opts) end
Add a constraint with the given name and args to the DDL for the table. See Sequel::Schema::CreateTableGenerator#constraint.
add_constraint(:valid_name, Sequel.like(:name, 'A%')) # ADD CONSTRAINT valid_name CHECK (name LIKE 'A%')
# File lib/sequel/database/schema_generator.rb, line 307 def add_constraint(name, *args, &block) @operations << {:op => :add_constraint, :name => name, :type => :check, :check => block || args} end
Add a foreign key with the given name and referencing the given table to the DDL for the table. See Sequel::Schema::CreateTableGenerator#column for the available options.
You can also pass an array of column names for creating composite foreign keys. In this case, it will assume the columns exist and will only add the constraint. You can provide a :name option to name the constraint.
NOTE: If you need to add a foreign key constraint to a single existing column use the composite key syntax even if it is only one column.
add_foreign_key(:artist_id, :table) # ADD COLUMN artist_id integer REFERENCES table add_foreign_key([:name], :table) # ADD FOREIGN KEY (name) REFERENCES table
PostgreSQL specific options:
Set to true to add the constraint with the NOT VALID syntax. This makes it so that future inserts must respect referential integrity, but allows the constraint to be added even if existing column values reference rows that do not exist. After all the existing data has been cleaned up, validate_constraint can be used to mark the constraint as valid. Note that this option only makes sense when using an array of columns.
# File lib/sequel/database/schema_generator.rb, line 343 def add_foreign_key(name, table, opts = {}) return add_composite_foreign_key(name, table, opts) if name.is_a?(Array) add_column(name, Integer, {:table=>table}.merge(opts)) end
Add a full text index on the given columns to the DDL for the table. See Sequel::Schema::CreateTableGenerator#index for available options.
# File lib/sequel/database/schema_generator.rb, line 350 def add_full_text_index(columns, opts = {}) add_index(columns, {:type=>:full_text}.merge(opts)) end
Add an index on the given columns to the DDL for the table. See Sequel::Schema::CreateTableGenerator#index for available options.
add_index(:artist_id) # CREATE INDEX table_artist_id_index ON table (artist_id)
# File lib/sequel/database/schema_generator.rb, line 358 def add_index(columns, opts = {}) @operations << {:op => :add_index, :columns => Array(columns)}.merge(opts) end
Add a primary key to the DDL for the table. See Sequel::Schema::CreateTableGenerator#column
for the available options. Like add_foreign_key
, if you
specify the column name as an array, it just creates a constraint:
add_primary_key(:id) # ADD COLUMN id serial PRIMARY KEY add_primary_key([:artist_id, :name]) # ADD PRIMARY KEY (artist_id, name)
# File lib/sequel/database/schema_generator.rb, line 368 def add_primary_key(name, opts = {}) return add_composite_primary_key(name, opts) if name.is_a?(Array) opts = @db.serial_primary_key_options.merge(opts) add_column(name, opts.delete(:type), opts) end
Add a spatial index on the given columns to the DDL for the table. See Sequel::Schema::CreateTableGenerator#index for available options.
# File lib/sequel/database/schema_generator.rb, line 376 def add_spatial_index(columns, opts = {}) add_index(columns, {:type=>:spatial}.merge(opts)) end
Add a unique constraint to the given column(s)
add_unique_constraint(:name) # ADD UNIQUE (name) add_unique_constraint(:name, :name=>:unique_name) # ADD CONSTRAINT unique_name UNIQUE (name)
Supports the same :deferrable option as Sequel::Schema::CreateTableGenerator#column.
# File lib/sequel/database/schema_generator.rb, line 317 def add_unique_constraint(columns, opts = {}) @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge(opts) end
Remove a column from the DDL for the table.
drop_column(:artist_id) # DROP COLUMN artist_id drop_column(:artist_id, :cascade=>true) # DROP COLUMN artist_id CASCADE
# File lib/sequel/database/schema_generator.rb, line 384 def drop_column(name, opts={}) @operations << {:op => :drop_column, :name => name}.merge(opts) end
Remove a constraint from the DDL for the table. MySQL/SQLite specific options:
Set the type of constraint to drop, either :primary_key, :foreign_key, or :unique.
drop_constraint(:unique_name) # DROP CONSTRAINT unique_name drop_constraint(:unique_name, :cascade=>true) # DROP CONSTRAINT unique_name CASCADE
# File lib/sequel/database/schema_generator.rb, line 395 def drop_constraint(name, opts={}) @operations << {:op => :drop_constraint, :name => name}.merge(opts) end
Remove an index from the DDL for the table. General options:
The name of the index to drop. If not given, uses the same name that would be used by #add_index with the same columns.
PostgreSQL specific options:
Cascade the index drop to dependent objects.
Drop the index using CONCURRENTLY, which doesn't block operations on the table. Supported in PostgreSQL 9.2+.
Only drop the index if it already exists.
drop_index(:artist_id) # DROP INDEX table_artist_id_index drop_index([:a, :b]) # DROP INDEX table_a_b_index drop_index([:a, :b], :name=>:foo) # DROP INDEX foo
# File lib/sequel/database/schema_generator.rb, line 414 def drop_index(columns, options={}) @operations << {:op => :drop_index, :columns => Array(columns)}.merge(options) end
Modify a column's name in the DDL for the table.
rename_column(:name, :artist_name) # RENAME COLUMN name TO artist_name
# File lib/sequel/database/schema_generator.rb, line 421 def rename_column(name, new_name, opts = {}) @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge(opts) end
Set a given column as allowing NULL values.
set_column_allow_null(:artist_name) # ALTER COLUMN artist_name DROP NOT NULL
# File lib/sequel/database/schema_generator.rb, line 446 def set_column_allow_null(name, allow_null=true) @operations << {:op => :set_column_null, :name => name, :null => allow_null} end
Modify a column's default value in the DDL for the table.
set_column_default(:artist_name, 'a') # ALTER COLUMN artist_name SET DEFAULT 'a'
# File lib/sequel/database/schema_generator.rb, line 428 def set_column_default(name, default) @operations << {:op => :set_column_default, :name => name, :default => default} end
Set a given column as not allowing NULL values.
set_column_not_null(:artist_name) # ALTER COLUMN artist_name SET NOT NULL
# File lib/sequel/database/schema_generator.rb, line 453 def set_column_not_null(name) set_column_allow_null(name, false) end
Modify a column's type in the DDL for the table.
set_column_type(:artist_name, 'char(10)') # ALTER COLUMN artist_name TYPE char(10)
PostgreSQL specific options:
Add a USING clause that specifies how to convert existing values to new values.
# File lib/sequel/database/schema_generator.rb, line 439 def set_column_type(name, type, opts={}) @operations << {:op => :set_column_type, :name => name, :type => type}.merge(opts) end