Module: ActiveRecord::Batches

### Home Classes Methods

### In Files

- lib/active_record/relation/batches.rb

### Methods

- #find_each
- #find_in_batches

### Files

- README.rdoc

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# ActiveRecord::Batches

### Public Instance Methods

find_each(options = {}) click to toggle source

Yields each record that was found by the find `options`. The find is performed by find_in_batches with a batch size of 1000 (or as specified by the `:batch_size` option).

Example:

    Person.where("age > 21").find_each do |person|
      person.party_all_night!
    end

Note: This method is only intended to use for batch processing of large amounts of records that wouldn't fit in memory all at once. If you just need to loop over less than 1000 records, it's probably better just to use the regular find methods.

    # File lib/active_record/relation/batches.rb, line 19
    def find_each(options = {})
      find_in_batches(options) do |records|
        records.each { |record| yield record }
      end
    end

find_in_batches(options = {}) click to toggle source

Yields each batch of records that was found by the find `options` as an array. The size of each batch is set by the `:batch_size` option; the default is 1000.

You can control the starting point for the batch processing by supplying the `:start` option. 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).

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 mean that this method only works with integer-based primary keys. You can't set the limit either, that's used to control the batch sizes.

Example:

    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! }
    end

    # File lib/active_record/relation/batches.rb, line 48
    def find_in_batches(options = {})
      relation = self

      unless arel.orders.blank? && arel.taken.blank?
        ActiveRecord::Base.logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
      end

      if (finder_options = options.except(:start, :batch_size)).present?
        raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order].present?
        raise "You can't specify a limit, it's forced to be the batch_size"  if options[:limit].present?

        relation = apply_finder_options(finder_options)
      end

      start = options.delete(:start)
      batch_size = options.delete(:batch_size) || 1000

      relation = relation.reorder(batch_order).limit(batch_size)
      records = start ? relation.where(table[primary_key].gteq(start)).to_a : relation.to_a

      while records.any?
        records_size = records.size
        primary_key_offset = records.last.id

        yield records

        break if records_size < batch_size

        if primary_key_offset
          records = relation.where(table[primary_key].gt(primary_key_offset)).to_a
        else
          raise "Primary key not included in the custom select clause"
        end
      end
    end

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