It's hard to say. It could be that most of the time is spend in the database - if so, you need to reconfigure/redesign your database/table/indices or query.

But there is one thing in your while loop that could suck up lots of resources, and that's the pushing onto @array_account. If there's a lot to be fetched from the database, @array_account will get huge - and because it grows by bits and pieces, a lot of allocation of memory will happen. That will take time, specially if you're using significant amounts of it. Do you actually need all the data into one array?