Hi,

I have a model Transaction for which I need to display the results of many calculations on many fields for a subset of transactions.

I've seen 2 ways to do it, but am not sure which is the best. I'm after the one that will have the least impact in terms of performance when data set grows and number of concurrent users increases.

data[:total_before] = Transaction.where(xxx).sum(:amount_before)
data[:total_after] = Transaction.where(xxx).sum(:amount_after)
...

or

transactions = Transaction.where(xxx)
data[:total_before]= transactions.inject(0) {|s, e| s + e.amount_before }
data[:total_after]= transactions.inject(0) {|s, e| s + e.amount_after }
...

Which one should I choose? (or is there a 3rd, better way?)

Thanks, P.