class Sequel::Schema::AlterTableGenerator
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.
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 376 def initialize(db, &block) 377 @db = db 378 @operations = [] 379 instance_exec(&block) if block 380 end
Public Instance Methods
Add a column with the given name, type, and opts. See CreateTableGenerator#column
for the available options (except for :index
, use a separate add_index
call to add an index for the column).
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 396 def add_column(name, type, opts = OPTS) 397 @operations << {:op => :add_column, :name => name, :type => type}.merge!(opts) 398 nil 399 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 408 def add_constraint(name, *args, &block) 409 opts = name.is_a?(Hash) ? name : {:name=>name} 410 @operations << opts.merge(:op=>:add_constraint, :type=>:check, :check=>block || args) 411 nil 412 end
Add a foreign key with the given name and referencing the given table. See CreateTableGenerator#column
for the available options (except for :index
, use a separate add_index
call to add an index for the column).
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 448 def add_foreign_key(name, table, opts = OPTS) 449 return add_composite_foreign_key(name, table, opts) if name.is_a?(Array) 450 add_column(name, Integer, {:table=>table}.merge!(opts)) 451 end
Add a full text index on the given columns. See CreateTableGenerator#index
for available options.
# File lib/sequel/database/schema_generator.rb 455 def add_full_text_index(columns, opts = OPTS) 456 add_index(columns, {:type=>:full_text}.merge!(opts)) 457 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)
Options:
- :name
-
Give a specific name for the index. Highly recommended if you plan on dropping the index later.
- :where
-
A filter expression, used to setup a partial index (if supported).
- :unique
-
Create a unique index.
PostgreSQL specific options:
- :concurrently
-
Create the index concurrently, so it doesn't require an exclusive lock on the table.
- :index_type
-
The underlying index type to use for a full_text index, gin by default).
- :language
-
The language to use for a full text index (simple by default).
- :opclass
-
Set an opclass to use for all columns (per-column opclasses require custom
SQL
). - :type
-
Set the index type (e.g. full_text, spatial, hash, gin, gist, btree).
- :if_not_exists
-
Only create the index if an index of the same name doesn't already exists
MySQL
specific options:
- :type
-
Set the index type, with full_text and spatial indexes handled specially.
Microsoft SQL
Server specific options:
- :include
-
Includes additional columns in the index.
- :key_index
-
Sets the KEY INDEX to the given value.
- :type
-
clustered uses a clustered index, full_text uses a full text index.
# File lib/sequel/database/schema_generator.rb 491 def add_index(columns, opts = OPTS) 492 @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts) 493 nil 494 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)
# File lib/sequel/database/schema_generator.rb 502 def add_primary_key(name, opts = OPTS) 503 return add_composite_primary_key(name, opts) if name.is_a?(Array) 504 opts = @db.serial_primary_key_options.merge(opts) 505 add_column(name, opts.delete(:type), opts) 506 end
Add a spatial index on the given columns. See CreateTableGenerator#index
for available options.
# File lib/sequel/database/schema_generator.rb 510 def add_spatial_index(columns, opts = OPTS) 511 add_index(columns, {:type=>:spatial}.merge!(opts)) 512 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
.
# File lib/sequel/database/schema_generator.rb 420 def add_unique_constraint(columns, opts = OPTS) 421 @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts) 422 nil 423 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 527 def drop_column(name, opts=OPTS) 528 @operations << {:op => :drop_column, :name => name}.merge!(opts) 529 nil 530 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 541 def drop_constraint(name, opts=OPTS) 542 @operations << {:op => :drop_constraint, :name => name}.merge!(opts) 543 nil 544 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 556 def drop_foreign_key(name, opts=OPTS) 557 if !name.is_a?(Array) && opts[:foreign_key_constraint_name] 558 opts = Hash[opts] 559 opts[:name] = opts[:foreign_key_constraint_name] 560 end 561 drop_composite_foreign_key(Array(name), opts) 562 drop_column(name) unless name.is_a?(Array) 563 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 580 def drop_index(columns, options=OPTS) 581 @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options) 582 nil 583 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 588 def rename_column(name, new_name, opts = OPTS) 589 @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts) 590 nil 591 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 629 def set_column_allow_null(name, allow_null=true) 630 @operations << {:op => :set_column_null, :name => name, :null => allow_null} 631 nil 632 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 603 def set_column_default(name, default) 604 @operations << {:op => :set_column_default, :name => name, :default => default} 605 nil 606 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 640 def set_column_not_null(name) 641 set_column_allow_null(name, false) 642 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 618 def set_column_type(name, type, opts=OPTS) 619 @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts) 620 nil 621 end
Private Instance Methods
Add a composite foreign key constraint
# File lib/sequel/database/schema_generator.rb 653 def add_composite_foreign_key(columns, table, opts) 654 @operations << {:op => :add_constraint, :type => :foreign_key, :columns => columns, :table => table}.merge!(opts) 655 nil 656 end
Add a composite primary key constraint
# File lib/sequel/database/schema_generator.rb 647 def add_composite_primary_key(columns, opts) 648 @operations << {:op => :add_constraint, :type => :primary_key, :columns => columns}.merge!(opts) 649 nil 650 end
Drop a composite foreign key constraint
# File lib/sequel/database/schema_generator.rb 659 def drop_composite_foreign_key(columns, opts) 660 @operations << opts.merge(:op => :drop_constraint, :type => :foreign_key, :columns => columns) 661 nil 662 end