class Cascading::Scope

Scope is a wrapper for a the private Cascading c.f.p.Scope object used to connect the dataflow graph by resolving fields. cascading.jruby wraps this facility so that it may be used to propagate field names at composition time (not Cascading plan time) in the same way they will later be propagated by the planner.

Attributes

scope[RW]

Public Instance Methods

copy() click to toggle source

Copy one Scope into another; relies upon the copy constructor of c.f.p.Scope.

# File lib/cascading/scope.rb, line 17
def copy
  Scope.new(Java::CascadingFlowPlanner::Scope.new(@scope))
end

grouping_fields() click to toggle source

The grouping fields of the Scope, which indicate the keys of an group/cogroup.

# File lib/cascading/scope.rb, line 57
def grouping_fields
  @scope.out_grouping_fields
end

to_s() click to toggle source

Prints a detailed description of this Scope, including its type and various selectors, fields, and key fields. Data is bubbled up directly from the Cascading c.f.p.Scope. This output can be useful for debugging the propagation of fields through your job (see Cascading::Flow#debug_scope and Cascading::Assembly#debug_scope, which both rely upon this method).

# File lib/cascading/scope.rb, line 66
    def to_s
      kind = 'Unknown'
      kind = 'Tap'   if @scope.tap?
      kind = 'Group' if @scope.group?
      kind = 'Each'  if @scope.each?
      kind = 'Every' if @scope.every?
      <<-END
Scope name: #{@scope.name}
  Kind: #{kind}
  Key selectors:     #{scope_fields_to_s(:key_selectors)}
  Sorting selectors: #{scope_fields_to_s(:sorting_selectors)}
  Remainder fields:  #{scope_fields_to_s(:remainder_fields)}
  Declared fields:   #{scope_fields_to_s(:declared_fields)}
  Arguments
    selector:   #{scope_fields_to_s(:arguments_selector)}
    declarator: #{scope_fields_to_s(:arguments_declarator)}
  Out grouping
    selector:   #{scope_fields_to_s(:out_grouping_selector)}
    fields:     #{scope_fields_to_s(:out_grouping_fields)}
    key fields: #{scope_fields_to_s(:key_selectors)}
  Out values
    selector: #{scope_fields_to_s(:out_values_selector)}
    fields:   #{scope_fields_to_s(:out_values_fields)}
END
    end

values_fields() click to toggle source

The values fields of the Scope, which indicate the fields in the current dataflow tuple.

# File lib/cascading/scope.rb, line 51
def values_fields
  @scope.out_values_fields
end

Public Class Methods

empty_scope(name) click to toggle source

Build an empty Scope, wrapping an empty c.f.p.Scope.

# File lib/cascading/scope.rb, line 27
def self.empty_scope(name)
  Scope.new(Java::CascadingFlowPlanner::Scope.new(name))
end

flow_scope(name) click to toggle source

Build a c.f.p.Scope for a Flow, which is empty except for its name.

# File lib/cascading/scope.rb, line 22
def self.flow_scope(name)
  Java::CascadingFlowPlanner::Scope.new(name)
end

new(scope) click to toggle source

Construct a Scope given the Cascading c.f.p.Scope to wrap.

# File lib/cascading/scope.rb, line 11
def initialize(scope)
  @scope = scope
end

outgoing_scope(flow_element, incoming_scopes) click to toggle source

Build a Scope for an arbitrary flow element. This is used to update the Scope at each stage in a pipe Assembly.

# File lib/cascading/scope.rb, line 44
def self.outgoing_scope(flow_element, incoming_scopes)
  java_scopes = incoming_scopes.compact.map{ |s| s.scope }
  Scope.new(outgoing_scope_for(flow_element, java.util.HashSet.new(java_scopes)))
end

source_scope(name, tap, flow_scope) click to toggle source

Build a Scope for a single source Tap. The ::flow_scope is propagated through this call into a new Scope.

# File lib/cascading/scope.rb, line 33
def self.source_scope(name, tap, flow_scope)
  incoming_scopes = java.util.HashSet.new
  incoming_scopes.add(flow_scope)
  java_scope = outgoing_scope_for(tap, incoming_scopes)
  # Taps and Pipes don't name their outgoing scopes like other FlowElements
  java_scope.name = name
  Scope.new(java_scope)
end