Ruby Datamapper left external connections

Question

Is there a way to make left external connections in Datamapper without resorting to a direct conversation with the data warehouse. I searched the net and the Datamapper document with failure in detail about how to do this.

Answer 1

Strict left outer joins seem to be pretty complicated.

Looking at the site:

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 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%") 

Looking at the docs , it looks like the Query class has a relationship handler that knows foreign keys.