Class: Alf::Engine::Materialize::Array

Inherits:
Object
  • Object
show all
Includes:
Cog
Defined in:
lib/alf-engine/alf/engine/materialize/array.rb

Overview

Provides in-memory materialization through a ruby Array.

This class acts as a Cog, that it, it is an enumerable of tuples. An optional ordering can be passed at construction.

Materialization occurs at prepare time, with auto-prepare on first access.

Example:

rel = [
  {:name => "Jones", :city => "London"},
  {:name => "Smith", :city => "Paris"},
  {:name => "Blake", :city => "London"}
]

Materialize::Array.new(rel).to_a
# => same as rel, in same order as the source

Materialize::Array.new(rel, Ordering[[:name, :asc]]).to_a
# => [
       {:name => "Blake", :city => "London"},
       {:name => "Jones", :city => "London"},
       {:name => "Smith", :city => "Paris"}
     ]

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Cog

#each, #to_dot, #to_relation

Constructor Details

#initialize(operand, ordering = nil) ⇒ Array

Creates a Materialize::Array instance



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 40

def initialize(operand, ordering = nil)
  @operand = operand
  @ordering = ordering
  @materialized = nil
end

Instance Attribute Details

#operand ⇒ Enumerable (readonly)

Returns The operand.

Returns:

  • (Enumerable) —

    The operand



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 34

def operand
  @operand
end

#ordering ⇒ Ordering (readonly)

Returns Ordering to ensure (optional).

Returns:

  • (Ordering) —

    Ordering to ensure (optional)



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 37

def ordering
  @ordering
end

Instance Method Details

#_each(&block) ⇒ Object 



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 47

def _each(&block)
  materialized.each(&block)
end

#clean ⇒ Object

Frees the materizalied hash



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 65

def clean
  @materialized = nil
end

#prepare ⇒ Object

Prepare through materialization of the operand as an ordered array



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# File 'lib/alf-engine/alf/engine/materialize/array.rb', line 54

def prepare
  @materialized ||= begin
    arr = operand.to_a
    arr.sort!(&ordering.sorter) if ordering
    arr
  end
end