Loop using count + modulo (when applicable) in Ruby

Question

To break up a long migration of data, I'm using a query limited to groups of 100, then processing those 100 records.

something like this...

count = Model.where("conditions").count
count = count / 100
count = count+1 if count%100 != 0
count.times do
  #do my data migration steps .limit(100)...
end

is there a shortcut or better way of doing that count based on whether or not there is a remainder when dividing by 100? Feels like I'm forgetting an easy way (besides rounding which seems slower, but maybe it's not).

user229044 · Accepted Answer · 2015-04-10 01:14:12Z

2

Yes. This is very well supported by Rails, you do not have to roll your own code for finding batches of records.

The easiest is to simply use find_each, which seamlessly loads 1000 records at a time:

Model.find_each do |model|
  # ...
end

The underlying mechanism is find_in_batches with a default batch size of 1000. You can use find_in_batches directly, but you do not have to, find_each is sufficient:

Model.find_in_batches(batch_size: 100) do |batch|
  batch.each do |model|
    # ...
  end
end

answered Apr 10, 2015 at 1:14

user229044♦

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1 Comment

creativereason Over a year ago

I knew there was something I was forgetting about that made this much easier. Thank you for such a detailed answer.

infused · Accepted Answer · 2015-04-10 01:15:52Z

1

Rails has several methods for loading records in batches. find_each would work nicely here. It defaults to batches of 1000, but you can specify the batch size:

Model.find_each(batch_size: 100) do |record|
  ...
end

answered Apr 10, 2015 at 1:15

infused

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