Class: Bmg::Operator::Matching

Inherits:
Object
  • Object
show all
Includes:
Binary
Defined in:
lib/bmg/operator/matching.rb

Overview

Matching operator.

Filters tuples of left operand to those matching at least one tuple in right operand.

Instance Attribute Summary

Attributes included from Bmg::Operator

#type

Instance Method Summary collapse

Methods included from Binary

#bind

Methods included from Bmg::Operator

#inspect, #to_s

Methods included from Relation

#_count, #bind, #count, #debug, #delete, empty, #empty?, #insert, new, #one, #one_or_nil, #to_csv, #to_json, #to_xlsx, #type, #update, #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, left, right, on) ⇒ Matching

Returns a new instance of Matching.



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# File 'lib/bmg/operator/matching.rb', line 12

def initialize(type, left, right, on)
  @type = type
  @left = left
  @right = right
  @on = on
end

Instance Method Details

#each ⇒ Object 



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# File 'lib/bmg/operator/matching.rb', line 25

def each
  return to_enum unless block_given?
  index = Hash.new
  right.each_with_object(index) do |t, index|
    key = tuple_project(t, on)
    index[key] = true
  end
  left.each do |tuple|
    key = tuple_project(tuple, on)
    yield tuple if index.has_key?(key)
  end
end

#to_ast ⇒ Object 



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

def to_ast
  [ :matching, left.to_ast, right.to_ast, on ]
end