datamapper multi-field unique index
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21-09-2019 - |
문제
In Datamapper, how would one specify the the combination of two fields must be unique. For example categories must have unique names within a domain:
class Category
include DataMapper.resource
property :name, String, :index=>true #must be unique for a given domain
belongs_to :domain
end
해결책
Did you try to define both properties as keys? Not sure I have tried it but that way they should become a composite key.
property :name, String, :key => true
property :category, Integer, :key => true
다른 팁
You have to create a unique index for the two properties:
class Category
include DataMapper::Resource
property :name, String, :unique_index => :u
property :domain_id, Integer, :unique_index => :u
belongs_to :domain
end
Actually, John, Joschi's answer is correct: the use of named :unique_index values does create a multiple-column index; it's important to read the right-hand side of those hash-rockets (i.e., if it had just been true
, you would be right).
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