Class: Axiom::Optimizer::Algebra::Projection::EmptyOperand

Inherits:

Axiom::Optimizer::Algebra::Projection

• Object
• Axiom::Optimizer
• Relation::Operation::Unary
• Axiom::Optimizer::Algebra::Projection
• Axiom::Optimizer::Algebra::Projection::EmptyOperand

Defined in:

lib/axiom/optimizer/algebra/projection.rb

Overview

Optimize when the operand is Empty

Constant Summary

Constants inherited from Axiom::Optimizer

Identity, VERSION

Instance Attribute Summary

Attributes inherited from Relation::Operation::Unary

#header

Attributes included from Function::Unary

#operand

Attributes inherited from Axiom::Optimizer

#operation

Instance Method Summary

• #optimizable? ⇒ Boolean private

  Test if the operand is empty.

• #optimize ⇒ Empty private

  Return a new Empty relation with the operation’s headers.

Methods inherited from Relation::Operation::Unary

#initialize

Methods included from Function::Unary

#initialize

Methods inherited from Axiom::Optimizer

chain, #initialize

Constructor Details

This class inherits a constructor from Axiom::Optimizer::Relation::Operation::Unary

Instance Method Details

#optimizable? ⇒ Boolean

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.

Test if the operand is empty

Returns:

• (Boolean)

# File 'lib/axiom/optimizer/algebra/projection.rb', line 168

def optimizable?
  operand.kind_of?(Axiom::Relation::Empty)
end

#optimize ⇒ Empty

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.

Return a new Empty relation with the operation’s headers

Returns:

• (Empty)

# File 'lib/axiom/optimizer/algebra/projection.rb', line 177

def optimize
  Axiom::Relation::Empty.new(header)
end