Class: Jrf::Stage

Inherits:
Object
  • Object
show all
Defined in:
lib/jrf/stage.rb

Defined Under Namespace

Classes: MapReducer, ReducerToken

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(block, src: nil) ⇒ Stage

Returns a new instance of Stage.



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# File 'lib/jrf/stage.rb', line 26

def initialize(block, src: nil)
  @src = src
  @reducers = []
  @cursor = 0
  @template = nil
  @mode = nil # nil=unknown, :reducer, :passthrough
  @map_transforms = {}
  @ctx = Class.new(RowContext) do
    define_method(:__jrf_expr__, &block)
  end.new
end

Instance Attribute Details

#src ⇒ Object (readonly)

Returns the value of attribute src.



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# File 'lib/jrf/stage.rb', line 11

def src
  @src
end

Class Method Details

.resolve_template(template, reducers) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 13

def self.resolve_template(template, reducers)
  if template.is_a?(ReducerToken)
    rows = reducers.fetch(template.index).finish
    rows.length == 1 ? rows.first : rows
  elsif template.is_a?(Array)
    template.map { |v| resolve_template(v, reducers) }
  elsif template.is_a?(Hash)
    template.transform_values { |v| resolve_template(v, reducers) }
  else
    template
  end
end

Instance Method Details

#call(input) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 38

def call(input)
  @ctx.reset(input)
  @cursor = 0
  @ctx.__jrf_current_stage = self
  result = @ctx.__jrf_expr__

  if @mode.nil?
    if @reducers.any?
      @mode = :reducer
      @template = result
    else
      @mode = :passthrough
    end
  end

  (@mode == :reducer) ? Control::DROPPED : result
end

#decomposable? ⇒ Boolean

Returns true if all reducers in this stage are DecomposableReduce instances, meaning partial accumulators from parallel workers can be merged.

Returns:

  • (Boolean) 


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# File 'lib/jrf/stage.rb', line 178

def decomposable?
  @mode == :reducer && @reducers.any? &&
    @reducers.all? { |r| r.is_a?(Reducers::DecomposableReduce) }
end

#finish ⇒ Object 



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# File 'lib/jrf/stage.rb', line 166

def finish
  return [] unless @mode == :reducer && @reducers.any?

  if @template.is_a?(ReducerToken)
    @reducers.fetch(@template.index).finish
  else
    [self.class.resolve_template(@template, @reducers)]
  end
end

#merge_partials!(other_partials) ⇒ Object

Merges an array of partial accumulators (from another worker) into this stage’s reducers.



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# File 'lib/jrf/stage.rb', line 196

def merge_partials!(other_partials)
  @reducers.each_with_index do |reducer, i|
    reducer.merge_partial(other_partials[i])
  end
end

#partial_accumulators ⇒ Object

Returns an array of raw accumulator values, one per reducer.



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# File 'lib/jrf/stage.rb', line 184

def partial_accumulators
  @reducers.map(&:partial)
end

#replace_accumulators!(partials) ⇒ Object

Replaces all reducer accumulators with the given values.



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# File 'lib/jrf/stage.rb', line 189

def replace_accumulators!(partials)
  @reducers.each_with_index do |reducer, i|
    reducer.instance_variable_set(:@acc, partials[i])
  end
end

#step_apply(collection, &block) ⇒ Object

Raises:

  • (TypeError) 


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# File 'lib/jrf/stage.rb', line 122

def step_apply(collection, &block)
  raise TypeError, "apply expects Array, got #{collection.class}" unless collection.is_a?(Array)

  apply_reducers = []
  template = nil
  results = []

  collection.each do |v|
    with_scoped_reducers(apply_reducers) do
      result = @ctx.send(:__jrf_with_current_input, v) { block.call(v) }
      template ||= result
      results << result
    end
  end

  if apply_reducers.any?
    self.class.resolve_template(template, apply_reducers)
  else
    results.each_with_object([]) do |mapped, arr|
      next if mapped.equal?(Control::DROPPED)
      if mapped.is_a?(Control::Flat)
        arr.concat(Array(mapped.value))
      else
        arr << mapped
      end
    end
  end
end

#step_group_by(key, &block) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 151

def step_group_by(key, &block)
  idx = @cursor
  map_reducer = (@reducers[idx] ||= MapReducer.new(:group_by, false))

  row = @ctx._
  slot = map_reducer.slot(key)
  with_scoped_reducers(slot.reducers) do
    result = @ctx.send(:__jrf_with_current_input, row) { block.call(row) }
    slot.template ||= result
  end

  @cursor += 1
  ReducerToken.new(idx)
end

#step_map(builtin, collection, &block) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 77

def step_map(builtin, collection, &block)
  idx = @cursor
  @cursor += 1

  if collection.is_a?(Array)
    raise TypeError, "map_values expects Hash, got Array" if builtin == :map_values
  elsif !collection.is_a?(Hash)
    raise TypeError, "#{builtin} expects #{builtin == :map_values ? "Hash" : "Array or Hash"}, got #{collection.class}"
  end

  # Transformation mode (detected on first call)
  if @map_transforms[idx]
    return transform_collection(builtin, collection, &block)
  end

  map_reducer = (@reducers[idx] ||= MapReducer.new(builtin, collection.is_a?(Array)))

  if collection.is_a?(Array)
    collection.each_with_index do |v, i|
      slot = map_reducer.slot(i)
      with_scoped_reducers(slot.reducers) do
        result = @ctx.send(:__jrf_with_current_input, v) { block.call(v) }
        slot.template ||= result
      end
    end
  else
    collection.each do |k, v|
      slot = map_reducer.slot(k)
      with_scoped_reducers(slot.reducers) do
        result = @ctx.send(:__jrf_with_current_input, v) { invoke_block(builtin, block, k, v) }
        slot.template ||= result
      end
    end
  end

  # Detect transformation: no reducers were allocated in any slot
  if @mode.nil? && map_reducer.slots.values.all? { |s| s.reducers.empty? }
    @map_transforms[idx] = true
    @reducers[idx] = nil
    return transformed_slots(builtin, map_reducer)
  end

  ReducerToken.new(idx)
end

#step_reduce(value, initial:, finish: nil, merge: nil, step_fn: nil, &step_block) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 56

def step_reduce(value, initial:, finish: nil, merge: nil, step_fn: nil, &step_block)
  idx = @cursor
  step_fn ||= step_block

  if @reducers[idx].nil?
    finish_rows = finish || ->(acc) { [acc] }
    @reducers[idx] = if merge
      Reducers.decomposable_reduce(initial, merge: merge, finish: finish_rows, &step_fn)
    else
      Reducers.reduce(initial, finish: finish_rows, &step_fn)
    end
    result = ReducerToken.new(idx)
  else
    result = Control::DROPPED
  end

  @reducers[idx].step(value)
  @cursor = idx + 1
  result
end