Class: ActiveRecord::ConnectionAdapters::PostgreSQLPrimaryKeyConstraint

Inherits:
PostgreSQLConstraint show all
Defined in:
lib/active_record/postgresql_extensions/constraints.rb

Overview

Creates PRIMARY KEY constraints for PostgreSQL tables and columns.

This class is meant to be used by PostgreSQL column and table definition and manipulation methods. There are several ways to create a PRIMARY KEY constraint:

  • on a table definition

  • on a column definition

  • when altering a table

ActiveRecord itself already provides some methods of creating PRIMARY KEYS, but we’ve added some PostgreSQL-specific extensions here. To override ActiveRecord’s built-in PRIMARY KEY generation, add an option for :id => false when creating the table via create_table.

When creating PRIMARY KEYs, you can use an options Hash to add various PostgreSQL-specific options as necessary or simply use a true statement to create a PRIMARY KEY on the column. Composite PRIMARY KEYs can also be created across multiple columns using a table definition or the PostgreSQLAdapter#add_primary_key method.

Column Definition

When creating a new table via PostgreSQLAdapter#create_table, you can specify PRIMARY KEY constraints on individual columns during definition.

Examples

create_table(:foo, :id => false) do |t|
  t.integer :foo_id, :primary_key => true
end

# Produces:
# CREATE TABLE "foo" (
#   "foo_id" integer,
#   PRIMARY KEY ("foo_id")
# );

create_table('foo', :id => false) do |t|
  t.integer :foo_id, :primary_key => {
    :tablespace => 'fubar',
    :index_parameters => 'FILLFACTOR=10'
  }
end

# Produces:
# CREATE TABLE "foo" (
#   "foo_id" integer,
#   PRIMARY KEY ("foo_id") WITH (FILLFACTOR=10) USING INDEX TABLESPACE "fubar"
# );

Table Definition

PRIMARY KEY constraints can also be applied to the table directly rather than on a column definition.

Examples

The following examples produces the same results as above:

create_table('foo', :id => false) do |t|
  t.integer :foo_id
  t.primary_key_constraint :foo_id
end

create_table('foo', :id => false) do |t|
  t.integer :foo_id
  t.primary_key_constraint :foo_id, {
    :tablespace => 'fubar',
    :index_parameters => 'FILLFACTOR=10'
  }
end

Table Manipulation

You can also create new PRIMARY KEY constraints outside of a table definition using PostgreSQLAdapter#add_primary_key or PostgreSQLAdapter#add_primary_key_constraint.

Examples

add_primary_key(:foo, :bar_id)
add_primary_key(:foo, [ :bar_id, :baz_id ])
add_primary_key(:foo, :bar_id, :name => 'foo_pk')
add_primary_key(:foo, :bar_id, :tablespace => 'fubar', :index_parameters => 'FILLFACTOR=10')

# Produces:
# ALTER TABLE "foo" ADD PRIMARY KEY ("bar_id");
# ALTER TABLE "foo" ADD PRIMARY KEY ("bar_id", "baz_id");
# ALTER TABLE "foo" ADD CONSTRAINT "foo_pk" PRIMARY KEY ("bar_id");
# ALTER TABLE "foo" ADD PRIMARY KEY ("bar_id") WITH (FILLFACTOR=10) USING INDEX TABLESPACE "fubar";

Options for PRIMARY KEY Constraints

  • :name - specifies a name for the constraint.

  • :storage_parameters - PostgreSQL allows you to add a couple of additional parameters to indexes to govern disk usage and such. This option is a simple String or a Hash that lets you insert these options as necessary. See the PostgreSQL documentation on index storage parameters for details. :index_parameters can also be used.

  • :tablespace - allows you to specify a tablespace for the index being created. See the PostgreSQL documentation on tablespaces for details.

Dropping PRIMARY KEY Constraints

Like all PostgreSQL constraints, you can use PostgreSQLAdapter#drop_constraint to remove a constraint from a table.

Instance Attribute Summary collapse

Attributes inherited from PostgreSQLConstraint

#base, #options

Instance Method Summary collapse

Methods included from PostgreSQLExtensions::Utils

#hash_or_array_of_hashes, #options_from_hash_or_string, #strip_heredoc

Constructor Details

#initialize(base, columns, options = {}) ⇒ PostgreSQLPrimaryKeyConstraint

:nodoc:



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# File 'lib/active_record/postgresql_extensions/constraints.rb', line 840

def initialize(base, columns, options = {}) #:nodoc:
  @columns = columns

  super(base, options)
end

Instance Attribute Details

#columns ⇒ Object

Returns the value of attribute columns.



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# File 'lib/active_record/postgresql_extensions/constraints.rb', line 838

def columns
  @columns
end

Instance Method Details

#to_sql ⇒ Object Also known as: to_s

:nodoc:



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# File 'lib/active_record/postgresql_extensions/constraints.rb', line 846

def to_sql #:nodoc:
  sql = String.new
  sql << "#{constraint_name}PRIMARY KEY "
  sql << "(" << Array.wrap(columns).collect { |column|
    base.quote_column_name(column)
  }.join(', ')
  sql << ")"
  sql << storage_parameters
  sql << using_tablespace
  sql
end