Class Sequel::Schema::AlterTableGenerator
In: lib/sequel/database/schema_generator.rb
Parent: Object

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

Attributes

operations  [R]  An array of DDL operations to perform

Public Class methods

Set the Database object to which to apply the DDL, and evaluate the block in the context of this object.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 329
329:       def initialize(db, &block)
330:         @db = db
331:         @operations = []
332:         instance_eval(&block) if block
333:       end

Public Instance methods

Add a column with the given name, type, and opts to the DDL for the table. 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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 348
348:       def add_column(name, type, opts = OPTS)
349:         @operations << {:op => :add_column, :name => name, :type => type}.merge!(opts)
350:       end

Add a constraint with the given name and args to the DDL for the table. 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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 359
359:       def add_constraint(name, *args, &block)
360:         opts = name.is_a?(Hash) ? name : {:name=>name}
361:         @operations << opts.merge(:op=>:add_constraint, :type=>:check, :check=>block || args)
362:       end

Add a foreign key with the given name and referencing the given table to the DDL for the 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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 396
396:       def add_foreign_key(name, table, opts = OPTS)
397:         return add_composite_foreign_key(name, table, opts) if name.is_a?(Array)
398:         add_column(name, Integer, {:table=>table}.merge!(opts))
399:       end

Add a full text index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 403
403:       def add_full_text_index(columns, opts = OPTS)
404:         add_index(columns, {:type=>:full_text}.merge!(opts))
405:       end

Add an index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

  add_index(:artist_id) # CREATE INDEX table_artist_id_index ON table (artist_id)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 411
411:       def add_index(columns, opts = OPTS)
412:         @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts)
413:       end

Add a primary key to the DDL for the table. 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)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 421
421:       def add_primary_key(name, opts = OPTS)
422:         return add_composite_primary_key(name, opts) if name.is_a?(Array)
423:         opts = @db.serial_primary_key_options.merge(opts)
424:         add_column(name, opts.delete(:type), opts)
425:       end

Add a spatial index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 429
429:       def add_spatial_index(columns, opts = OPTS)
430:         add_index(columns, {:type=>:spatial}.merge!(opts))
431:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 370
370:       def add_unique_constraint(columns, opts = OPTS)
371:         @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts)
372:       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

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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 446
446:       def drop_column(name, opts=OPTS)
447:         @operations << {:op => :drop_column, :name => name}.merge!(opts)
448:       end

Remove a constraint from the DDL for the table. MySQL/SQLite specific options:

:type :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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 457
457:       def drop_constraint(name, opts=OPTS)
458:         @operations << {:op => :drop_constraint, :name => name}.merge!(opts)
459:       end

Remove a foreign key and the associated column from the DDL for 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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 471
471:       def drop_foreign_key(name, opts=OPTS)
472:         drop_composite_foreign_key(Array(name), opts)
473:         drop_column(name) unless name.is_a?(Array)
474:       end

Remove an index from the DDL for 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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 491
491:       def drop_index(columns, options=OPTS)
492:         @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options)
493:       end

Modify a column‘s name in the DDL for the table.

  rename_column(:name, :artist_name) # RENAME COLUMN name TO artist_name

[Source]

     # File lib/sequel/database/schema_generator.rb, line 498
498:       def rename_column(name, new_name, opts = OPTS)
499:         @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts)
500:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 536
536:       def set_column_allow_null(name, allow_null=true)
537:         @operations << {:op => :set_column_null, :name => name, :null => allow_null}
538:       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'

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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 512
512:       def set_column_default(name, default)
513:         @operations << {:op => :set_column_default, :name => name, :default => default}
514:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 546
546:       def set_column_not_null(name)
547:         set_column_allow_null(name, false)
548:       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:

: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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 526
526:       def set_column_type(name, type, opts=OPTS)
527:         @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts)
528:       end

[Validate]