Thanks Marnen. I think the times are only related to the time taken to execute the SQL query, not to put that in memory and then sort the array.
In the first case, I'm curious about how MySQL can sort all the elements so fast. I've read (http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/) that Ruby's Array sort method implementation is pretty good. It uses Quick Sort. I've tried to to sort an array of strings an another one of integers, already sorted both of them, with *irb* and the result it's almost instantaneous. Maybe MySQL uses quick sort too.. About the second query you say it has to sort the users in the opposite order which MySQL should take the same amount of time than before, but this is not the case. I see what you mean about Ruby, but I think that time is only for MySQL. About the third and fourth queries, I've compared both results with queries one and two and I get the same array. Why would the DB return the records in an unpredictable order? In the Wikipedia <http://en.wikipedia.org/wiki/Quicksort>, the right sidebar explains the reason why Quick Sort is slow when the set is already sorted. Oh, this is also a pretty nice website<http://www.sorting-algorithms.com/reversed-initial-order>, it has animations of different sort algorithms. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
