6/25/2018 - 7:29 AM

Split operation to parts (batch) in Rails

# find_in_batches(options = {}) public
#Yields each batch of records that was found by the find options as an array.

Person.where("age > 21").find_in_batches do |group|
  sleep(50) # Make sure it doesn't get too crowded in there!
  group.each { |person| person.party_all_night! }

# If you do not provide a block to #find_in_batches, it will return an Enumerator for chaining with other methods:

Person.find_in_batches.with_index do |group, batch|
  puts "Processing group ##{batch}"

# To be yielded each record one by one, use #find_each instead.

# Options
# :batch_size - Specifies the size of the batch. Default to 1000.

# :start - Specifies the starting point for the batch processing.

# This is especially useful if you want multiple workers dealing with the same processing queue. You can make worker 1 handle all the records between id 0 and 10,000 and worker 2 handle from 10,000 and beyond (by setting the :start option on that worker).

# Let's process the next 2000 records

Person.find_in_batches(start: 2000, batch_size: 2000) do |group|
  group.each { |person| person.party_all_night! }

# NOTE: It’s not possible to set the order. That is automatically set to ascending on the primary key (“id ASC”) to make the batch ordering work. This also means that this method only works with integer-based primary keys.

# NOTE: You can’t set the limit either, that’s used to control the batch sizes.