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, #count, #debug, empty, #empty?, new, #one, #one_or_nil, #to_csv, #to_json, #to_xlsx, #type, #visit, #with_type, #with_type_attrlist, #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, #minus, #not_matching, #page, #project, #rename, #restrict, #spied, #summarize, #transform, #ungroup, #union, #unspied, #unwrap

Methods included from Algebra::Shortcuts

#cross_product, #exclude, #image, #images, #join, #left_join, #matching, #not_matching, #prefix, #rxmatch, #suffix, #ungroup, #unwrap, #where

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

#_count ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 67

def _count
  operand._count
end

#delete(predicate = Predicate.tautology) ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 57

def delete(predicate = Predicate.tautology)
  operand.delete(predicate)
end

#each ⇒ Object 



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

def each
  return to_enum unless block_given?
  @operand.each do |tuple|
    yield rename_tuple(tuple, renaming)
  end
end

#insert(arg) ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 38

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

#to_ast ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 61

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

#update(arg, predicate = Predicate.tautology) ⇒ Object 



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# File 'lib/bmg/operator/rename.rb', line 48

def update(arg, predicate = Predicate.tautology)
  case arg
  when Hash
    operand.update(rename_tuple(arg, reverse_renaming), predicate)
  else
    super
  end
end