Class: Mongoid::MapReduce::Reducer

Inherits:
Object
  • Object
show all
Defined in:
lib/mongoid/mapreduce/reducer.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(klass, selector, options) ⇒ Reducer

Initialize the reducer with given values

klass - Mongoid model Class selector - Selector to use for search (often from criteria) options - Hash of options:

count_field - Name of field used to store count in results
formula - Name of formula to be used (underscore)
map_key - Name of field used as key in map function

Returns nothing



21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
 
# File 'lib/mongoid/mapreduce/reducer.rb', line 21

def initialize(klass, selector, options)
  options[:klass] = klass
  options[:selector] = selector
  options[:formula] ||= :aggregate_fields

  @klass = klass
  @selector = selector
  @formula_name = options[:formula]
  @options = options
  @fields = {}

  if options.key?(:fields)
    options[:fields].each do |f|
      field f.to_sym
    end
  end
end

Instance Attribute Details

#count_field ⇒ Object

Returns the value of attribute count_field.



9
10
11
 
# File 'lib/mongoid/mapreduce/reducer.rb', line 9

def count_field
  @count_field
end

Instance Method Details

#field(sym, options = {}) ⇒ Object

Adds a field to the map/reduce operation

sym - String or Symbol, name of field to add

Returns nothing.



57
58
59
60
 
# File 'lib/mongoid/mapreduce/reducer.rb', line 57

def field(sym, options={})
  options[:type] ||= Integer
  @fields[sym.to_sym] = options
end

#formula ⇒ Object

Expose the currently selected formula, from instance variable if possible.

Returns Formula object.



42
43
44
45
46
47
48
49
50
 
# File 'lib/mongoid/mapreduce/reducer.rb', line 42

def formula
  # Find and initialize our formula
  klass = "Mongoid::MapReduce::Formula::#{@formula_name.to_s.camelize}"
  begin
    @formula ||= klass.constantize.new(@fields, @options)
  rescue NameError
    raise "Could not load formula for #{klass}"
  end
end

#run ⇒ Object

Runs the map/reduce operation and returns the result

Returns Mongoid::MapReduce::Results object (array) containing Mongoid::MapReduce::Document objects (hashes)



66
67
68
69
70
71
72
73
74
 
# File 'lib/mongoid/mapreduce/reducer.rb', line 66

def run
  begin
    coll = @klass.collection.map_reduce(formula.map, formula.reduce, { query: @selector, out: "#map_reduce" } ).find.to_a
  rescue
    raise "Error: could not execute map reduce function"
  end

  formula.process(coll)
end