Class: Sequel::Schema::AlterTableGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/sequel/database/schema_generator.rb

Overview

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.

Direct Known Subclasses

Postgres::AlterTableGenerator

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(db, &block) ⇒ AlterTableGenerator

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



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# File 'lib/sequel/database/schema_generator.rb', line 433

def initialize(db, &block)
  @db = db
  @operations = []
  instance_exec(&block) if block
end

Instance Attribute Details

#operations ⇒ Object (readonly)

An array of operations to perform



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# File 'lib/sequel/database/schema_generator.rb', line 429

def operations
  @operations
end

Instance Method Details

#add_column(name, type, opts = OPTS) ⇒ Object

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



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# File 'lib/sequel/database/schema_generator.rb', line 452

def add_column(name, type, opts = OPTS)
  op = {:op => :add_column, :name => name, :type => type}.merge!(opts)
  index_opts = op.delete(:index)
  @operations << op
  add_index(name, index_opts.is_a?(Hash) ? index_opts : OPTS) if index_opts
  nil
end

#add_constraint(name, *args, &block) ⇒ Object

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



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# File 'lib/sequel/database/schema_generator.rb', line 467

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) ⇒ Object

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.



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# File 'lib/sequel/database/schema_generator.rb', line 516

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) ⇒ Object

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



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# File 'lib/sequel/database/schema_generator.rb', line 523

def add_full_text_index(columns, opts = OPTS)
  add_index(columns, {:type=>:full_text}.merge!(opts))
end

#add_index(columns, opts = OPTS) ⇒ Object

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)



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# File 'lib/sequel/database/schema_generator.rb', line 531

def add_index(columns, opts = OPTS)
  @operations << {:op => :add_index, :columns => Array(columns)}.merge!(opts)
  nil
end

#add_primary_key(name, opts = OPTS) ⇒ Object

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:

:include

Include additional columns in the underlying index, to allow for index-only scans in more cases (PostgreSQL 11+).

:using_index

Use the USING INDEX clause to specify an existing unique index

:without_overlaps

Use WITHOUT OVERLAPS clause to specify an exclusion constraint on the final column (PostgreSQL 18+, composite primary keys only).



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# File 'lib/sequel/database/schema_generator.rb', line 550

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) ⇒ Object

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



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# File 'lib/sequel/database/schema_generator.rb', line 558

def add_spatial_index(columns, opts = OPTS)
  add_index(columns, {:type=>:spatial}.merge!(opts))
end

#add_unique_constraint(columns, opts = OPTS) ⇒ Object

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:

:include

Include additional columns in the underlying index, to allow for index-only scans in more cases (PostgreSQL 11+).

:nulls_not_distinct

Use NULLS NOT DISTINCT to setup a constraint where NULL entries are considered distinct (PostgreSQL 15+)

:using_index

Use the USING INDEX clause to specify an existing unique index

:without_overlaps

Use WITHOUT OVERLAPS clause to specify an exclusion constraint on the final column (PostgreSQL 18+, composite unique constraints only).



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# File 'lib/sequel/database/schema_generator.rb', line 489

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) ⇒ Object

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.



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# File 'lib/sequel/database/schema_generator.rb', line 575

def drop_column(name, opts=OPTS)
  @operations << {:op => :drop_column, :name => name}.merge!(opts)
  nil
end

#drop_constraint(name, opts = OPTS) ⇒ Object

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.



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# File 'lib/sequel/database/schema_generator.rb', line 589

def drop_constraint(name, opts=OPTS)
  @operations << {:op => :drop_constraint, :name => name}.merge!(opts)
  nil
end

#drop_foreign_key(name, opts = OPTS) ⇒ Object

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



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# File 'lib/sequel/database/schema_generator.rb', line 604

def drop_foreign_key(name, opts=OPTS)
  if !name.is_a?(Array) && opts[:foreign_key_constraint_name]
    opts = Hash[opts]
    opts[:name] = opts[:foreign_key_constraint_name]
  end
  drop_composite_foreign_key(Array(name), opts)
  drop_column(name) unless name.is_a?(Array)
end

#drop_index(columns, options = OPTS) ⇒ Object

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 628

def drop_index(columns, options=OPTS)
  @operations << {:op => :drop_index, :columns => Array(columns)}.merge!(options)
  nil
end

#rename_column(name, new_name, opts = OPTS) ⇒ Object

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 636

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) ⇒ Object

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 677

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) ⇒ Object

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 651

def set_column_default(name, default)
  @operations << {:op => :set_column_default, :name => name, :default => default}
  nil
end

#set_column_not_null(name) ⇒ Object

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 688

def set_column_not_null(name)
  set_column_allow_null(name, false)
end

#set_column_type(name, type, opts = OPTS) ⇒ Object

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 666

def set_column_type(name, type, opts=OPTS)
  @operations << {:op => :set_column_type, :name => name, :type => type}.merge!(opts)
  nil
end