How to update or insert on Sequel dataset?

Question

I just started using Sequel in a really small Sinatra app. Since I've got only one DB table, I don't need to use models.

I want to update a record if it exists or insert a new record if it does not. I came up with the following solution:

  rec = $nums.where(:number => n, :type => t)
  if $nums.select(1).where(rec.exists)
    rec.update(:counter => :counter + 1)
  else
    $nums.insert(:number => n, :counter => 1, :type => t)
  end

Where $nums is DB[:numbers] dataset.

I believe that this way isn't the most elegant implementation of "update or insert" behavior.

How should it be done?

Answer 1

You should probably not check before updating/inserting; because:

1. This is an extra db call.
2. This could introduce a race condition.

What you should do instead is to test the return value of update:

rec = $nums.where(:number => n, :type => t)
if 1 != rec.update(:counter => :counter + 1)
  $nums.insert(:number => n, :counter => 1, :type => t)
end