My solution works, but I wonder if there is a better one.
I have a model (:cards), which has a foreign key :box_id. I am
interested in the id's of those cards which have a certain box_id.
Currently I assume that I can easily hold an array of all thos :cards in
memory (i.e. no cursor needed).
This is my current solution:
Card.where(box_id: params[:box_id]).map {|c| c.id }.each do |cid|
# .... Do something with cid
end
This is compact, but I don't like the fact that first, all data from the
retrieved Card objects needs to be stored in memory at least temporarily
(there is even a 'text' field in Card!), but only the id is needed.
I thought as an alternative to use find_by_sql, but the API
documentation warns that this should be only used as a "last resort",
because it makes us dependent on the syntax for a particular database.
Although in my case, the SQL query would be so simple that I don't fear
I would run into compatibility problems when exchanging one database for
another, I wonder whether there is a simpler solution, using just
ActiveRecord functions.
Ronald
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