class Sequel::Schema::AlterTableGenerator
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.
Attributes
An array of operations to perform
Public Class Methods
Set the Database object to which to apply the changes, and evaluate the block in the context of this object.
# File lib/sequel/database/schema_generator.rb, line 386 def initialize(db, &block) @db = db @operations = [] instance_exec(&block) if block end
Public Instance Methods
Add a column with the given name, type, and opts. See Sequel::Schema::CreateTableGenerator#column for the available options.
add_column(:name, String) # ADD COLUMN name varchar(255)
PostgreSQL specific options:
- :if_not_exists
-
Set to true to not add the column if it already exists (PostgreSQL 9.6+)
MySQL specific options:
- :after
-
The name of an existing column that the new column should be positioned after
- :first
-
Create this new column before all other existing columns
# File lib/sequel/database/schema_generator.rb, line 405 def add_column(name, type, opts = OPTS) op = {:op => :add_column, :name => name, :type => type}.merge!(opts) index_opts = op.delete(:index) @operations << op add_index(name, index_opts.is_a?(Hash) ? index_opts : OPTS) if index_opts nil end
Add a constraint with the given name and args. See Sequel::Schema::CreateTableGenerator#constraint.
add_constraint(:valid_name, Sequel.like(:name, 'A%')) # ADD CONSTRAINT valid_name CHECK (name LIKE 'A%' ESCAPE '\') add_constraint({name: :valid_name, deferrable: true}, Sequel.like(:name, 'A%')) # ADD CONSTRAINT valid_name CHECK (name LIKE 'A%' ESCAPE '\') DEFERRABLE INITIALLY DEFERRED
# File lib/sequel/database/schema_generator.rb, line 420 def add_constraint(name, *args, &block) opts = name.is_a?(Hash) ? name : {:name=>name} @operations << opts.merge(:op=>:add_constraint, :type=>:check, :check=>block || args) nil end
Add a foreign key with the given name and referencing the given 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:
- :not_valid
-
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 459 def add_foreign_key(name, table, opts = 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. See Sequel::Schema::CreateTableGenerator#full_text_index for available options.
# File lib/sequel/database/schema_generator.rb, line 466 def add_full_text_index(columns, opts = OPTS) add_index(columns, {:type=>:full_text}.merge!(opts)) end
Add an index on the given columns. 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 474 def add_index(columns, opts = OPTS) @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts) nil end
Add a primary key. 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 485 def add_primary_key(name, opts = 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. See Sequel::Schema::CreateTableGenerator#index for available options.
# File lib/sequel/database/schema_generator.rb, line 493 def add_spatial_index(columns, opts = 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 432 def add_unique_constraint(columns, opts = OPTS) @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts) nil end
Remove a column from the table.
drop_column(:artist_id) # DROP COLUMN artist_id drop_column(:artist_id, cascade: true) # DROP COLUMN artist_id CASCADE
Options:
- :cascade
-
CASCADE the operation, dropping other objects that depend on the dropped column.
PostgreSQL specific options:
- :if_exists
-
Use IF EXISTS, so no error is raised if the column does not exist.
# File lib/sequel/database/schema_generator.rb, line 510 def drop_column(name, opts=OPTS) @operations << {:op => :drop_column, :name => name}.merge!(opts) nil end
Remove a constraint from the table:
drop_constraint(:unique_name) # DROP CONSTRAINT unique_name drop_constraint(:unique_name, cascade: true) # DROP CONSTRAINT unique_name CASCADE
MySQL/SQLite specific options:
- :type
-
Set the type of constraint to drop, either :primary_key, :foreign_key, or :unique.
# File lib/sequel/database/schema_generator.rb, line 524 def drop_constraint(name, opts=OPTS) @operations << {:op => :drop_constraint, :name => name}.merge!(opts) nil end
Remove a foreign key and the associated column from the table. General options:
- :name
-
The name of the constraint to drop. If not given, uses the same name that would be used by #add_foreign_key with the same columns.
NOTE: If you want to drop only the foreign key constraint but keep the column, use the composite key syntax even if it is only one column.
drop_foreign_key(:artist_id) # DROP CONSTRAINT table_artist_id_fkey, DROP COLUMN artist_id drop_foreign_key([:name]) # DROP CONSTRAINT table_name_fkey
# File lib/sequel/database/schema_generator.rb, line 539 def drop_foreign_key(name, opts=OPTS) if !name.is_a?(Array) && opts[:foreign_key_constraint_name] opts = Hash[opts] opts[:name] = opts[:foreign_key_constraint_name] end drop_composite_foreign_key(Array(name), opts) drop_column(name) unless name.is_a?(Array) end
Remove an index from the table. General options:
- :name
-
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
-
Cascade the index drop to dependent objects.
- :concurrently
-
Drop the index using CONCURRENTLY, which doesn't block operations on the table. Supported in PostgreSQL 9.2+.
- :if_exists
-
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 563 def drop_index(columns, options=OPTS) @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options) nil end
Rename one of the table's columns.
rename_column(:name, :artist_name) # RENAME COLUMN name TO artist_name
# File lib/sequel/database/schema_generator.rb, line 571 def rename_column(name, new_name, opts = OPTS) @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts) nil end
Set a given column as allowing NULL values.
set_column_allow_null(:artist_name) # ALTER COLUMN artist_name DROP NOT NULL
On MySQL, make sure to use a symbol for the name of the column, as otherwise you can lose the default and type for the column.
# File lib/sequel/database/schema_generator.rb, line 612 def set_column_allow_null(name, allow_null=true) @operations << {:op => :set_column_null, :name => name, :null => allow_null} nil end
Modify the default value for one of the table's column.
set_column_default(:artist_name, 'a') # ALTER COLUMN artist_name SET DEFAULT 'a'
To remove an existing default value, use nil
as the value:
set_column_default(:artist_name, nil) # ALTER COLUMN artist_name SET DEFAULT NULL
On MySQL, make sure to use a symbol for the name of the column, as otherwise you can lose the type and NULL/NOT NULL setting for the column.
# File lib/sequel/database/schema_generator.rb, line 586 def set_column_default(name, default) @operations << {:op => :set_column_default, :name => name, :default => default} nil end
Set a given column as not allowing NULL values.
set_column_not_null(:artist_name) # ALTER COLUMN artist_name SET NOT NULL
On MySQL, make sure to use a symbol for the name of the column, as otherwise you can lose the default and type for the column.
# File lib/sequel/database/schema_generator.rb, line 623 def set_column_not_null(name) set_column_allow_null(name, false) end
Modify the type of one of the table's column.
set_column_type(:artist_name, 'char(10)') # ALTER COLUMN artist_name TYPE char(10)
PostgreSQL specific options:
- :using
-
Add a USING clause that specifies how to convert existing values to new values.
On MySQL, make sure to use a symbol for the name of the column, as otherwise you can lose the default and NULL/NOT NULL setting for the column.
# File lib/sequel/database/schema_generator.rb, line 601 def set_column_type(name, type, opts=OPTS) @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts) nil end
Private Instance Methods
Add a composite foreign key constraint
# File lib/sequel/database/schema_generator.rb, line 636 def add_composite_foreign_key(columns, table, opts) @operations << {:op => :add_constraint, :type => :foreign_key, :columns => columns, :table => table}.merge!(opts) nil end
Add a composite primary key constraint
# File lib/sequel/database/schema_generator.rb, line 630 def add_composite_primary_key(columns, opts) @operations << {:op => :add_constraint, :type => :primary_key, :columns => columns}.merge!(opts) nil end
Drop a composite foreign key constraint
# File lib/sequel/database/schema_generator.rb, line 642 def drop_composite_foreign_key(columns, opts) @operations << opts.merge(:op => :drop_constraint, :type => :foreign_key, :columns => columns) nil end