Class: Axiom::Relation::Operation::Group

Inherits:
Axiom::Relation show all
Includes:
Unary
Defined in:
lib/axiom/relation/operation/group.rb

Overview

A class representing a grouped relation

Defined Under Namespace

Modules: Methods

Instance Attribute Summary collapse

Attributes included from Operation::Unary

#operand

Attributes inherited from Axiom::Relation

#header

Instance Method Summary collapse

Methods inherited from Axiom::Relation

#==, #[], #directions, #empty?, #include?, #materialize, #materialized?, new, #replace

Methods included from Visitable

#accept

Constructor Details

#initialize(operand, name, attributes) ⇒ undefined

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Initialize a grouped relation

Parameters:



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# File 'lib/axiom/relation/operation/group.rb', line 28

def initialize(operand, name, attributes)
  super(operand)
  inner      = header.project(attributes)
  @outer     = header - inner
  @attribute = Attribute::Relation.new(name, header: inner)
  @header    = @outer.extend(attribute)
end

Instance Attribute Details

#attribute ⇒ Attribute::Relation (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The grouped attribute

Returns:



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# File 'lib/axiom/relation/operation/group.rb', line 17

def attribute
  @attribute
end

Instance Method Details

#each {|tuple| ... } ⇒ self

Iterate over each tuple in the set

Examples:

grouped = Group.new(operand, name, attributes)
grouped.each { |tuple| ... }

Yields:

  • (tuple)

Yield Parameters:

  • tuple (Tuple) —

    each tuple in the set

Returns:

  • (self) 


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# File 'lib/axiom/relation/operation/group.rb', line 50

def each
  return to_enum unless block_given?
  build_index.each do |outer_tuple, inner_tuples|
    inner_relation = attribute.new_relation(inner_tuples)
    yield outer_tuple.extend(header, [inner_relation])
  end
  self
end