What is wrong with code like User.find (: all) .each?

Question

I just read this requirement in the job list:

Aware of the pitfalls of code like: User.find(:all).each

I immediately realized that I was unqualified for this job, because in my life I do not understand what the problem is. It...

• is the design connected? Should I store the database query in a variable and then iterate over it?
• dangerous?
• too verbose? Should I use User.all.eachinstead? (-1 word! W00t!)
• just poorly worded? If this is preceded by a "user table has 3 million rows"?

Answer 1

, "", , , - User.all.each, :

User.all.each do |u|
    next if !u.is_active
    ...
end

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Answer 2

User.all . 3 , 3 . . SQL , , , " "

Answer 3

? User.all.each? (-1 ! W00t!)

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Answer 4

, , , , , . , , :

User.find_in_batches do |group|
  group.each do |user|
    user.do_something
  end
end

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Answer 5

Well, if you want to sound reasonable, you answer: "There is no trap for this question, assuming that you want to change or display the values ​​from each of the user objects. :-)