Class: EachBatch::PluckedBatchEnumerator

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/each_batch/plucked_batch_enumerator.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(relation, of:, order:, keys:, pluck_keys:) ⇒ PluckedBatchEnumerator

Returns a new instance of PluckedBatchEnumerator.



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 10

def initialize(relation, of:, order:, keys:, pluck_keys:)
  if pluck_keys.present? && (pluck_keys & keys).to_set != keys.to_set
    raise ArgumentError, 'Not all keys are included in the custom select clause for pluck'
  end

  @relation = relation
  @of = of
  @order = order
  @keys = keys
  @pluck_keys = pluck_keys
  @key_indices = keys.map { |key| pluck_keys.index(key) }
end

Instance Attribute Details

#keys ⇒ Object (readonly)

Returns the value of attribute keys.



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 8

def keys
  @keys
end

#order ⇒ Object (readonly)

Returns the value of attribute order.



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 8

def order
  @order
end

#relation ⇒ Object (readonly)

Returns the value of attribute relation.



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 8

def relation
  @relation
end

Instance Method Details

#batch_size ⇒ Object 



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 23

def batch_size
  @of
end

#each ⇒ Object 



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 27

def each
  return self unless block_given?

  batch_relation = relation.reorder(keys.product([order]).to_h).limit(batch_size)
  batch_relation.skip_query_cache! # Retaining the results in the query cache would undermine the point of batching

  yielded_relation = batch_relation
  op = order.to_s.casecmp('desc').zero? ? :lt : :gt
  last_idx = batch_size - 1

  pk = relation.primary_key.to_sym
  single_pluck_key = @pluck_keys.length == 1


  loop do
    results = yielded_relation.pluck(*@pluck_keys)

    break if results.empty?

    yield results

    # grab the offsets from the plucked results
    offsets =
      if single_pluck_key
        results[last_idx]
      else
        results[last_idx]&.values_at(*@key_indices)
      end

    break if offsets.nil?

    yielded_relation = batch_relation.where_row(*keys).public_send(op, *offsets)
  end
end

#each_row(&block) ⇒ Object 



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# File 'lib/each_batch/plucked_batch_enumerator.rb', line 62

def each_row(&block)
  return to_enum(:each_row) unless block_given?

  each { |row_batch| row_batch.each(&block) }
end