Class: Bmg::Operator::Rename

Inherits:
Object
  • Object
show all
Includes:
Unary
Defined in:
lib/bmg/operator/rename.rb

Overview

Rename operator.

Rename some attribute of input tuples, according to a renaming Hash.

Example:

[{ a: 1, b: 2 }] rename {:b => :c} => [{ a: 1, c: 2 }]

Keys of the renaming Hash SHOULD be existing attributes of the input tuples. Values of the renaming Hash SHOULD NOT be existing attributes of the input tuples.

Instance Attribute Summary

Attributes included from Bmg::Operator

#type

Instance Method Summary collapse

Methods included from Unary

#bind

Methods included from Bmg::Operator

#inspect, #to_s

Methods included from Relation

#bind, #debug, empty, #empty?, new, #one, #one_or_nil, #to_csv, #to_json, #visit, #with_typecheck, #without_typecheck, #y_by_x, #ys_by_x

Methods included from Algebra

#allbut, #autosummarize, #autowrap, #constants, #extend, #group, #image, #join, #left_join, #matching, #materialize, #not_matching, #page, #project, #restrict, #spied, #summarize, #transform, #union, #unspied

Methods included from Algebra::Shortcuts

#image, #join, #left_join, #matching, #not_matching, #prefix, #rxmatch, #suffix

Constructor Details

#initialize(type, operand, renaming) ⇒ Rename

Returns a new instance of Rename.



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# File 'lib/bmg/operator/rename.rb', line 19

def initialize(type, operand, renaming)
  @type = type
  @operand = operand
  @renaming = renaming
end

Instance Method Details

#delete ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 55

def delete
  operand.delete
end

#each ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 31

def each
  @operand.each do |tuple|
    yield rename(tuple, renaming)
  end
end

#insert(arg) ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 37

def insert(arg)
  case arg
  when Hash       then operand.insert(rename(arg, reverse_renaming))
  when Relation   then operand.insert(arg.rename(reverse_renaming))
  when Enumerable then operand.insert(arg.map{|t| rename(t, reverse_renaming) })
  else
    super
  end
end

#to_ast ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 59

def to_ast
  [ :rename, operand.to_ast, renaming.dup ]
end

#update(arg) ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 47

def update(arg)
  case arg
  when Hash then operand.update(rename(arg, reverse_renaming))
  else
    super
  end
end