Inconsistent order of columns in SQL WHERE clause in dynamic finders and scopes

Me too. I think that the first 2 examples should generate SQL as in the last one.

The middle one is impossible to fix since you're passing a hash which by definition is unordered. This best that can be done in this case is to sort predictably, which it appears to do alphabetically. The first one is essentially the same as the second one since that is what it called eventually after the name has been split up into the constituent parts.

You could fix the first one by changing find_by_attributes in ActiveRecord::FinderMethods to chain calls to where rather building a hash and then calling where but there may be a performance impact so that'd need to be checked.

Why not just create a named scope and exclusively use that?

  scope :find_by_city_then_category, lambda { |city, category| where(:city_id => city).where(:category_id => category) }

It turns out that all methods generate the same query on Ruby 1.9 where hashes are ordered. I'm using 1.8.7 and that's why it generates different queries.

Instead of

Venue.find_all_by_city_id_and_category_id(1, 1)

you can also do

Venue.scoped_by_city_id_and_category_id(1, 1)

The advantage is that scoped_by creates a method after each time it is called. So next time method_missing will not be called and performance will be better. find_by does not do anything like that and would continue to hit method_missing every single time.

Not directly related to this ticket but just wanted to let people know about it.