Composite primary key created with a 'property' and 'belongs_to' declaration requires property to be unique

[jdarais]

It seems DataMapper doesn't behave properly when a composite key is split between a foreign key declared with 'belongs_to' and a second, non-unique column declared with 'property'.

Example:

class Person
    include DataMapper::Resource

    property :id,   Integer,    :key => true
    has n, :aliases
end

class Alias
    include DataMapper::Resource

    property :alias_num,    Integer,    :key => true
    property :alias,        String
    belongs_to :person, :key => true
end

personA = Person.new(:id => 1)
personA.aliases.new(:alias_num => 1, :alias => 'Geoffery')
personA.save

personB = Person.new(:id => 2)
personB.aliases.new(:alias_num => 1, :alias => 'Richard')
personB.save

results in error: "column alias_num is not unique"

When 'alias_num' is not required to be unique because it is part of a composite key. Currently, the erroneous behavior can be circumvented by also adding a property declaration to match the belongs_to declaration:

class Alias
    include DataMapper::Resource

    property :alias_num,    Integer,    :key => true
    property :alias,        String
    property :person_id,     Integer,    :key => true
    belongs_to :person, :key => true
end

But it seems like such an extra declaration shouldn't be necessary

[HQ063]

instead of adding the association_id property, you can add :unique_index=>false to the column declared with property

class Alias
    include DataMapper::Resource

    property :alias_num,    Integer,    :key => true, :unique_index => false
    property :alias,        String
    belongs_to :person, :key => true
end