Ruby Datamapperは外部結合を残しました

Question

データストアに直接話すことに頼ることなく、Datamapperで左外部結合を行う方法はありますか？私はネットとDatamapperの文書を検索してきました。

Answer 1

厳密な左外部結合がかなり難しいようです。 Queryクラスは、外部キーを認識している関係ハンドラを持っているように見えるdocsを見てみると

68 # QueryPaths can be used to construct joins in a very declarative manner. 
69 # 
70 # Starting from a root model, you can call any relationship by its name. 
71 # The returned object again responds to all property and relationship names 
72 # that are defined in the relationship's target model. 
73 # 
74 # This means that you can walk the chain of available relationships, and  then 
75 # match against a property at the end of that chain. The object returned by 
76 # the last call to a property name also responds to all the comparison 
77 # operators available in traditional queries. This makes for some powerful 
78 # join construction! 
79 # 
80 Customer.all(Customer.orders.order_lines.item.sku.like => "%BLUE%") 

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