Schema::AlterTableGenerator
is an internal class that the user is not expected to instantiate directly. Instances are created by 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.
Methods
Public Class
Public Instance
Attributes
operations | [R] |
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 401 def initialize(db, &block) 402 @db = db 403 @operations = [] 404 instance_exec(&block) if block 405 end
Public Instance methods
Add a column with the given name, type, and opts. See 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 420 def add_column(name, type, opts = OPTS) 421 op = {:op => :add_column, :name => name, :type => type}.merge!(opts) 422 index_opts = op.delete(:index) 423 @operations << op 424 add_index(name, index_opts.is_a?(Hash) ? index_opts : OPTS) if index_opts 425 nil 426 end
Add a constraint with the given name and args. See 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 435 def add_constraint(name, *args, &block) 436 opts = name.is_a?(Hash) ? name : {:name=>name} 437 @operations << opts.merge(:op=>:add_constraint, :type=>:check, :check=>block || args) 438 nil 439 end
Add a foreign key with the given name and referencing the given table. See 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 478 def add_foreign_key(name, table, opts = OPTS) 479 return add_composite_foreign_key(name, table, opts) if name.is_a?(Array) 480 add_column(name, Integer, {:table=>table}.merge!(opts)) 481 end
Add a full text index on the given columns. See CreateTableGenerator#full_text_index
for available options.
# File lib/sequel/database/schema_generator.rb 485 def add_full_text_index(columns, opts = OPTS) 486 add_index(columns, {:type=>:full_text}.merge!(opts)) 487 end
Add an index on the given columns. See 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 493 def add_index(columns, opts = OPTS) 494 @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts) 495 nil 496 end
Add a primary key. See 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)
PostgreSQL specific options:
:using_index |
Use the USING INDEX clause to specify an existing unique index |
# File lib/sequel/database/schema_generator.rb 508 def add_primary_key(name, opts = OPTS) 509 return add_composite_primary_key(name, opts) if name.is_a?(Array) 510 opts = @db.serial_primary_key_options.merge(opts) 511 add_column(name, opts.delete(:type), opts) 512 end
Add a spatial index on the given columns. See CreateTableGenerator#index
for available options.
# File lib/sequel/database/schema_generator.rb 516 def add_spatial_index(columns, opts = OPTS) 517 add_index(columns, {:type=>:spatial}.merge!(opts)) 518 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 CreateTableGenerator#column
.
PostgreSQL specific options:
:using_index |
Use the USING INDEX clause to specify an existing unique index |
# File lib/sequel/database/schema_generator.rb 451 def add_unique_constraint(columns, opts = OPTS) 452 @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts) 453 nil 454 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 533 def drop_column(name, opts=OPTS) 534 @operations << {:op => :drop_column, :name => name}.merge!(opts) 535 nil 536 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 547 def drop_constraint(name, opts=OPTS) 548 @operations << {:op => :drop_constraint, :name => name}.merge!(opts) 549 nil 550 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 |
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 562 def drop_foreign_key(name, opts=OPTS) 563 if !name.is_a?(Array) && opts[:foreign_key_constraint_name] 564 opts = Hash[opts] 565 opts[:name] = opts[:foreign_key_constraint_name] 566 end 567 drop_composite_foreign_key(Array(name), opts) 568 drop_column(name) unless name.is_a?(Array) 569 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 |
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 586 def drop_index(columns, options=OPTS) 587 @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options) 588 nil 589 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 594 def rename_column(name, new_name, opts = OPTS) 595 @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts) 596 nil 597 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 635 def set_column_allow_null(name, allow_null=true) 636 @operations << {:op => :set_column_null, :name => name, :null => allow_null} 637 nil 638 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 609 def set_column_default(name, default) 610 @operations << {:op => :set_column_default, :name => name, :default => default} 611 nil 612 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 646 def set_column_not_null(name) 647 set_column_allow_null(name, false) 648 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 624 def set_column_type(name, type, opts=OPTS) 625 @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts) 626 nil 627 end