Can this Ruby on Rails code be optimized or improved at all?
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The code:

    user = ... #pretend it has a value :)
    instances = Array.new
    Product.all.each do |product|
        productInstance = ProductInstance.new
        productInstance.user = user
        productInstance.product = product
        instances.push(productInstance)
    end

`Product` and `ProductInstance` are both Rails models. Is a for-each loop on `Product.all` going to be slow? Just wondering if there is a better way of doing this...