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 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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 349
349:       def initialize(db, &block)
350:         @db = db
351:         @operations = []
352:         instance_exec(&block) if block
353:       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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 368
368:       def add_column(name, type, opts = OPTS)
369:         @operations << {:op => :add_column, :name => name, :type => type}.merge!(opts)
370:         nil
371:       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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 380
380:       def add_constraint(name, *args, &block)
381:         opts = name.is_a?(Hash) ? name : {:name=>name}
382:         @operations << opts.merge(:op=>:add_constraint, :type=>:check, :check=>block || args)
383:         nil
384:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 419
419:       def add_foreign_key(name, table, opts = OPTS)
420:         return add_composite_foreign_key(name, table, opts) if name.is_a?(Array)
421:         add_column(name, Integer, {:table=>table}.merge!(opts))
422:       end

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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 426
426:       def add_full_text_index(columns, opts = OPTS)
427:         add_index(columns, {:type=>:full_text}.merge!(opts))
428:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 462
462:       def add_index(columns, opts = OPTS)
463:         @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts)
464:         nil
465:       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)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 473
473:       def add_primary_key(name, opts = OPTS)
474:         return add_composite_primary_key(name, opts) if name.is_a?(Array)
475:         opts = @db.serial_primary_key_options.merge(opts)
476:         add_column(name, opts.delete(:type), opts)
477:       end

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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 481
481:       def add_spatial_index(columns, opts = OPTS)
482:         add_index(columns, {:type=>:spatial}.merge!(opts))
483:       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 392
392:       def add_unique_constraint(columns, opts = OPTS)
393:         @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts)
394:         nil
395:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 498
498:       def drop_column(name, opts=OPTS)
499:         @operations << {:op => :drop_column, :name => name}.merge!(opts)
500:         nil
501:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 512
512:       def drop_constraint(name, opts=OPTS)
513:         @operations << {:op => :drop_constraint, :name => name}.merge!(opts)
514:         nil
515:       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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 527
527:       def drop_foreign_key(name, opts=OPTS)
528:         if !name.is_a?(Array) && opts[:foreign_key_constraint_name]
529:           opts = Hash[opts]
530:           opts[:name] = opts[:foreign_key_constraint_name]
531:         end
532:         drop_composite_foreign_key(Array(name), opts)
533:         drop_column(name) unless name.is_a?(Array)
534:       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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 551
551:       def drop_index(columns, options=OPTS)
552:         @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options)
553:         nil
554:       end

Rename one of the table‘s columns.

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

[Source]

     # File lib/sequel/database/schema_generator.rb, line 559
559:       def rename_column(name, new_name, opts = OPTS)
560:         @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts)
561:         nil
562:       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 600
600:       def set_column_allow_null(name, allow_null=true)
601:         @operations << {:op => :set_column_null, :name => name, :null => allow_null}
602:         nil
603:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 574
574:       def set_column_default(name, default)
575:         @operations << {:op => :set_column_default, :name => name, :default => default}
576:         nil
577:       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 611
611:       def set_column_not_null(name)
612:         set_column_allow_null(name, false)
613:       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.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 589
589:       def set_column_type(name, type, opts=OPTS)
590:         @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts)
591:         nil
592:       end

[Validate]