[MONGOID-4522] Make #any? not retrieve entire result set, like #exists? - MongoDB Jira

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Release Notes:
any? on has_many associations no longer retrieves the entire association from the database. This makes any? more efficient in most cases, but repeated calls to any? when the association is not loaded will query the database on every call.
Backwards Compatibility:
Minor Change

I have a simple class:

class Article

  include Mongoid::Document

end

Here are some simple queries with the mongo query made:

Article.criteria.any?

=> {"find"=>"articles", "filter"=>{}}

Article.criteria.exists? # or empty? or blank? or present?

=> {"find"=>"articles", "filter"=>{}, "projection"=>{"_id"=>1}, "limit"=>1}

I couldn't find the reason why any? is not optimized like the other methods. Is there an explanation? And can we improve this?

is related to

MONGOID-4830 Remove #one method from has_many associations

MONGOID-4959 Document any? in tutorial

related to

MONGOID-4890 Destroying model instances with dependent associations in transactions raises OperationFailure due to use of (deprecated) count

links to