class Sequel::Schema::AlterTableGenerator

  1. lib/sequel/database/schema_generator.rb
Superclass: Object

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

operations [R]

An array of operations to perform

Public Class methods

new (db, &block)

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

[show source]
# File lib/sequel/database/schema_generator.rb, line 343
def initialize(db, &block)
  @db = db
  @operations = []
  instance_exec(&block) if block
end

Public Instance methods

add_column (name, type, opts = OPTS)

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

[show source]
# File lib/sequel/database/schema_generator.rb, line 362
def add_column(name, type, opts = OPTS)
  @operations << {:op => :add_column, :name => name, :type => type}.merge!(opts)
  nil
end
add_constraint (name, *args, &block)

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
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# File lib/sequel/database/schema_generator.rb, line 374
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_foreign_key (name, table, opts = OPTS)

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.

[show source]
# File lib/sequel/database/schema_generator.rb, line 413
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_full_text_index (columns, opts = OPTS)

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

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# File lib/sequel/database/schema_generator.rb, line 420
def add_full_text_index(columns, opts = OPTS)
  add_index(columns, {:type=>:full_text}.merge!(opts))
end
add_index (columns, opts = OPTS)

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)

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.

[show source]
# File lib/sequel/database/schema_generator.rb, line 456
def add_index(columns, opts = OPTS)
  @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts)
  nil
end
add_primary_key (name, opts = OPTS)

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)
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# File lib/sequel/database/schema_generator.rb, line 467
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_spatial_index (columns, opts = OPTS)

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

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# File lib/sequel/database/schema_generator.rb, line 475
def add_spatial_index(columns, opts = OPTS)
  add_index(columns, {:type=>:spatial}.merge!(opts))
end
add_unique_constraint (columns, opts = OPTS)

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.

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# File lib/sequel/database/schema_generator.rb, line 386
def add_unique_constraint(columns, opts = OPTS)
  @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge!(opts)
  nil
end
drop_column (name, opts=OPTS)

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.

[show source]
# File lib/sequel/database/schema_generator.rb, line 492
def drop_column(name, opts=OPTS)
  @operations << {:op => :drop_column, :name => name}.merge!(opts)
  nil
end
drop_constraint (name, opts=OPTS)

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.

[show source]
# File lib/sequel/database/schema_generator.rb, line 506
def drop_constraint(name, opts=OPTS)
  @operations << {:op => :drop_constraint, :name => name}.merge!(opts)
  nil
end
drop_foreign_key (name, opts=OPTS)

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
[show source]
# File lib/sequel/database/schema_generator.rb, line 521
def drop_foreign_key(name, opts=OPTS)
  drop_composite_foreign_key(Array(name), opts)
  drop_column(name) unless name.is_a?(Array)
end
drop_index (columns, options=OPTS)

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
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# File lib/sequel/database/schema_generator.rb, line 541
def drop_index(columns, options=OPTS)
  @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options)
  nil
end
rename_column (name, new_name, opts = OPTS)

Rename one of the table's columns.

rename_column(:name, :artist_name) # RENAME COLUMN name TO artist_name
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# File lib/sequel/database/schema_generator.rb, line 549
def rename_column(name, new_name, opts = OPTS)
  @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge!(opts)
  nil
end
set_column_allow_null (name, allow_null=true)

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.

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# File lib/sequel/database/schema_generator.rb, line 590
def set_column_allow_null(name, allow_null=true)
  @operations << {:op => :set_column_null, :name => name, :null => allow_null}
  nil
end
set_column_default (name, default)

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.

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# File lib/sequel/database/schema_generator.rb, line 564
def set_column_default(name, default)
  @operations << {:op => :set_column_default, :name => name, :default => default}
  nil
end
set_column_not_null (name)

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.

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# File lib/sequel/database/schema_generator.rb, line 601
def set_column_not_null(name)
  set_column_allow_null(name, false)
end
set_column_type (name, type, opts=OPTS)

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.

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# File lib/sequel/database/schema_generator.rb, line 579
def set_column_type(name, type, opts=OPTS)
  @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts)
  nil
end