Mike Mike - 1 month ago 7
Ruby Question

How do I extract a field from an array of my models in order to form a single query?

I’m using Rails 4.2.7. I have an array of my model objects and currently I’m iterating through that array to find matching entries in the database based on a field my each object …

my_object_times.each_with_index do |my_object_time, index|
found_my_object_time = MyObjectTime.find_by_my_object_id_and_overall_rank(my_object_id, my_object_time.overall_rank)


My question is, how can I rewrite the above to run one query instead of N queries, if N is the size of the array. What I wanted was to force my underlying database (PostGres 9.5) to do a “IF VALUE IN (…)” type of query but I’m not sure how to extract all the attributes from my array and then pass them in appropriately to a query.

Answer

I would do something like this:

found_my_object_times = MyObjectTime.where(
  object_id: my_object_id, 
  overall_rank: my_object_times.map(&:overall_rank)
)