Class: JoinByPathsHelper

Inherits:
Set
  • Object
show all
Defined in:
lib/sequel/plugins/join_by_paths.rb

Constant Summary collapse

EMPTY_ARRAY = 
[].freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(smodel) ⇒ JoinByPathsHelper

Returns a new instance of JoinByPathsHelper.



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# File 'lib/sequel/plugins/join_by_paths.rb', line 84

def initialize(smodel)
  super()
  @start_model = smodel
end

Instance Attribute Details

#result ⇒ Object (readonly)

Returns the value of attribute result.



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# File 'lib/sequel/plugins/join_by_paths.rb', line 79

def result
  @result
end

#start_model ⇒ Object (readonly)

Returns the value of attribute start_model.



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# File 'lib/sequel/plugins/join_by_paths.rb', line 80

def start_model
  @start_model
end

Instance Method Details

#add(path_str) ⇒ Object 



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# File 'lib/sequel/plugins/join_by_paths.rb', line 190

def add(path_str)
  super(QPath.new(@start_model, path_str))
end

#build_unique_join_segments ⇒ Object 



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# File 'lib/sequel/plugins/join_by_paths.rb', line 89

def build_unique_join_segments
  return (@result = EMPTY_ARRAY) if empty?

  maxlen = map(&:size).max
  iset = nil
  @result = []

  (0...maxlen).each do |i|
    iset = Set.new
    each { |qp| (iset << qp.segments[i]) if qp.segments[i] }
    @result << iset
  end

  many_to_many_count = 0 # counter for differing multiple
  # many_to_many through alias
  @result.map! do |jseg|
    jseg.map  do |seg|
      leftm = seg.first.model_class
      assoc = leftm.association_reflection(seg.last.to_sym)

      rightm = seg.last.model_class
      # cf.  documentation in sequel/model/associations.rb
      case assoc[:type]
      # :many_to_one :: Foreign key in current model's table points to
      #                 associated model's primary key.
      when :many_to_one
        lks = [assoc[:key]].flatten
        rks = [rightm.primary_key].flatten

      when :one_to_many, :one_to_one
        # :one_to_many :: Foreign key in associated model's table points to this
        #                 model's primary key.
        # :one_to_one :: Similar to one_to_many in terms of foreign keys, but
        #                only one object is associated to the current object through the
        #                association.
        lks = [leftm.primary_key].flatten
        rks = [assoc[:key]].flatten

      when :many_to_many, :one_through_one
        #  :many_to_many :: A join table is used that has a foreign key that points
        #                  to this model's primary key and a foreign key that points to the
        #                  associated model's primary key.  Each current model object can be
        #                  associated with many associated model objects, and each associated
        #                  model object can be associated with many current model objects.
        # TODO: testcase for  :one_through_one
        # when    # :one_through_one :: Similar to many_to_many in terms of foreign keys, but only one object
        #                     is associated to the current object through the association.
        #                     Provides only getter methods, no setter or modification methods.

        result_ = []

        # in case of multiple many_to_many rels, we need differing through aliases
        many_to_many_count = many_to_many_count + 1
        through_alias = "t#{many_to_many_count}".to_sym

        # For many_to_many first we add the join with assigment table
        lks_ = [assoc[:left_primary_key]].flatten
        rks_ = [assoc[:left_key]].flatten

        lks_.map! { |k| Sequel[seg.first.alias_sym][k] } unless seg.first.empty?
        rks_.map! { |k| Sequel[through_alias][k] }

        result_ << {
          type: assoc[:type],
          left: leftm.table_name,
          right: assoc[:join_table],
          alias: through_alias,
          cond: rks_.zip(lks_).to_h
        }

        # then we add the join with with target table (right)
        lks = [assoc[:right_key]].flatten
        rks = [assoc.right_primary_key].flatten

        lks.map! { |k| Sequel[through_alias][k] }
        rks.map! { |k| Sequel[seg.last.alias_sym][k] }

        result_ << {
          type: assoc[:type],
          left: assoc[:join_table],
          right: rightm.table_name,
          alias: seg.last.alias_sym,
          cond: rks.zip(lks).to_h
        }

        next result_

      end

      lks.map! { |k| Sequel[seg.first.alias_sym][k] } unless seg.first.empty?
      rks.map! { |k| Sequel[seg.last.alias_sym][k] }

      { type: assoc[:type],
        left: leftm.table_name,
        right: rightm.table_name,
        alias: seg.last.alias_sym,
        cond: rks.zip(lks).to_h }
    end
  end
end

#dataset(start_dtset = nil) ⇒ Object 



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# File 'lib/sequel/plugins/join_by_paths.rb', line 194

def dataset(start_dtset = nil)
  start_dataset = (start_dtset || @start_model.dataset)
  return start_dataset if empty?

  build_unique_join_segments
  need_distinct = false
  ret = @result.flatten.inject(start_dataset) do |dt, jo|
    need_distinct = true if jo[:type] == :many_to_many
    dt.left_join(Sequel[jo[:right]].as(jo[:alias]),
                 jo[:cond],
                 implicit_qualifier: jo[:left])
  end
  need_distinct ? ret.distinct : ret
end

#join_by_paths_helper(*pathlist) ⇒ Object 



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# File 'lib/sequel/plugins/join_by_paths.rb', line 209

def join_by_paths_helper(*pathlist)
  pathlist.each { |path_str| add path_str }
  self
end