Module: DataMapper::Constraints::Adapters::DataObjectsAdapter

Includes:
SQL
Included in:
MysqlAdapter, OracleAdapter, PostgresAdapter, SqlserverAdapter
Defined in:
lib/data_mapper/constraints/adapters/do_adapter.rb

Defined Under Namespace

Modules: SQL

Instance Method Summary collapse

Instance Method Details

#constraint_exists?(storage_name, constraint_name) ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Determine if a constraint exists for a table

Parameters:

  • storage_name (Symbol) —

    name of table to check constraint on

  • constraint_name (~String) —

    name of constraint to check for

Returns:

  • (Boolean) 


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# File 'lib/data_mapper/constraints/adapters/do_adapter.rb', line 17

def constraint_exists?(storage_name, constraint_name)
  statement = DataMapper::Ext::String.compress_lines(<<-SQL)
    SELECT COUNT(*)
    FROM #{quote_name('information_schema')}.#{quote_name('table_constraints')}
    WHERE #{quote_name('constraint_type')} = 'FOREIGN KEY'
    AND #{quote_name('table_schema')} = ?
    AND #{quote_name('table_name')} = ?
    AND #{quote_name('constraint_name')} = ?
  SQL

  select(statement, schema_name, storage_name, constraint_name).first > 0
end

#create_relationship_constraint(relationship) ⇒ true, false

Create the constraint for a relationship

Parameters:

  • relationship (Relationship) —

    the relationship to create the constraint for

Returns:

  • (true, false) —

    true if creating the constraints was successful



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# File 'lib/data_mapper/constraints/adapters/do_adapter.rb', line 40

def create_relationship_constraint(relationship)
  return false unless valid_relationship_for_constraint?(relationship)

  source_storage_name = relationship.source_model.storage_name(name)
  target_storage_name = relationship.target_model.storage_name(name)
  constraint_name     = constraint_name(source_storage_name, relationship.name)

  return false if constraint_exists?(source_storage_name, constraint_name)

  constraint_type =
    case relationship.inverse.constraint
    when :protect            then 'NO ACTION'
    # TODO: support :cascade as an option:
    #   (destroy doesn't communicate the UPDATE constraint)
    when :destroy, :destroy! then 'CASCADE'
    when :set_nil            then 'SET NULL'
    end

  return false if constraint_type.nil?

  source_keys = relationship.source_key.map { |p| property_to_column_name(p, false) }
  target_keys = relationship.target_key.map { |p| property_to_column_name(p, false) }

  create_constraints_statement = create_constraints_statement(
    constraint_name,
    constraint_type,
    source_storage_name,
    source_keys,
    target_storage_name,
    target_keys)

  execute(create_constraints_statement)
end

#destroy_relationship_constraint(relationship) ⇒ true, false

Remove the constraint for a relationship

Parameters:

  • relationship (Relationship) —

    the relationship to remove the constraint for

Returns:

  • (true, false) —

    true if destroying the constraint was successful



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# File 'lib/data_mapper/constraints/adapters/do_adapter.rb', line 84

def destroy_relationship_constraint(relationship)
  return false unless valid_relationship_for_constraint?(relationship)

  storage_name    = relationship.source_model.storage_name(name)
  constraint_name = constraint_name(storage_name, relationship.name)

  return false unless constraint_exists?(storage_name, constraint_name)

  destroy_constraints_statement =
    destroy_constraints_statement(storage_name, constraint_name)

  execute(destroy_constraints_statement)
end