Class: Sequel::Model::Associations::EagerGraphLoader

Inherits:
Object
  • Object
show all
Defined in:
lib/sequel/model/associations.rb

Overview

This class is the internal implementation of eager_graph. It is responsible for taking an array of plain hashes and returning an array of model objects with all eager_graphed associations already set in the association cache.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(dataset) ⇒ EagerGraphLoader

Initialize all of the data structures used during loading.



2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
 
# File 'lib/sequel/model/associations.rb', line 2616

def initialize(dataset)
  opts = dataset.opts
  eager_graph = opts[:eager_graph]
  @master =  eager_graph[:master]
  requirements = eager_graph[:requirements]
  reflection_map = @reflection_map = eager_graph[:reflections]
  reciprocal_map = @reciprocal_map = eager_graph[:reciprocals]
  limit_map = @limit_map = eager_graph[:limits]
  @unique = eager_graph[:cartesian_product_number] > 1
      
  alias_map = @alias_map = {}
  type_map = @type_map = {}
  after_load_map = @after_load_map = {}
  reflection_map.each do |k, v|
    alias_map[k] = v[:name]
    after_load_map[k] = v[:after_load] unless v[:after_load].empty?
    type_map[k] = if v.returns_array?
      true
    elsif (limit_and_offset = limit_map[k]) && !limit_and_offset.last.nil?
      :offset
    end
  end

  # Make dependency map hash out of requirements array for each association.
  # This builds a tree of dependencies that will be used for recursion
  # to ensure that all parts of the object graph are loaded into the
  # appropriate subordinate association.
  @dependency_map = {}
  # Sort the associations by requirements length, so that
  # requirements are added to the dependency hash before their
  # dependencies.
  requirements.sort_by{|a| a[1].length}.each do |ta, deps|
    if deps.empty?
      dependency_map[ta] = {}
    else
      deps = deps.dup
      hash = dependency_map[deps.shift]
      deps.each do |dep|
        hash = hash[dep]
      end
      hash[ta] = {}
    end
  end
      
  # This mapping is used to make sure that duplicate entries in the
  # result set are mapped to a single record.  For example, using a
  # single one_to_many association with 10 associated records,
  # the main object column values appear in the object graph 10 times.
  # We map by primary key, if available, or by the object's entire values,
  # if not. The mapping must be per table, so create sub maps for each table
  # alias.
  records_map = {@master=>{}}
  alias_map.keys.each{|ta| records_map[ta] = {}}
  @records_map = records_map

  datasets = opts[:graph][:table_aliases].to_a.reject{|ta,ds| ds.nil?}
  column_aliases = opts[:graph_aliases] || opts[:graph][:column_aliases]
  primary_keys = {}
  column_maps = {}
  models = {}
  row_procs = {}
  datasets.each do |ta, ds|
    models[ta] = ds.model
    primary_keys[ta] = []
    column_maps[ta] = {}
    row_procs[ta] = ds.row_proc
  end
  column_aliases.each do |col_alias, tc|
    ta, column = tc
    column_maps[ta][col_alias] = column
  end
  column_maps.each do |ta, h|
    pk = models[ta].primary_key
    if pk.is_a?(Array)
      primary_keys[ta] = []
      h.select{|ca, c| primary_keys[ta] << ca if pk.include?(c)}
    else
      h.select{|ca, c| primary_keys[ta] = ca if pk == c}
    end
  end
  @column_maps = column_maps
  @primary_keys = primary_keys
  @row_procs = row_procs

  # For performance, create two special maps for the master table,
  # so you can skip a hash lookup.
  @master_column_map = column_maps[master]
  @master_primary_keys = primary_keys[master]

  # Add a special hash mapping table alias symbols to 5 element arrays that just
  # contain the data in other data structures for that table alias.  This is
  # used for performance, to get all values in one hash lookup instead of
  # separate hash lookups for each data structure.
  ta_map = {}
  alias_map.keys.each do |ta|
    ta_map[ta] = [records_map[ta], row_procs[ta], alias_map[ta], type_map[ta], reciprocal_map[ta]]
  end
  @ta_map = ta_map
end

Instance Attribute Details

#after_load_map ⇒ Object (readonly)

Hash with table alias symbol keys and after_load hook values



2573
2574
2575
 
# File 'lib/sequel/model/associations.rb', line 2573

def after_load_map
  @after_load_map
end

#alias_map ⇒ Object (readonly)

Hash with table alias symbol keys and association name values



2576
2577
2578
 
# File 'lib/sequel/model/associations.rb', line 2576

def alias_map
  @alias_map
end

#column_maps ⇒ Object (readonly)

Hash with table alias symbol keys and subhash values mapping column_alias symbols to the symbol of the real name of the column



2580
2581
2582
 
# File 'lib/sequel/model/associations.rb', line 2580

def column_maps
  @column_maps
end

#dependency_map ⇒ Object (readonly)

Recursive hash with table alias symbol keys mapping to hashes with dependent table alias symbol keys.



2583
2584
2585
 
# File 'lib/sequel/model/associations.rb', line 2583

def dependency_map
  @dependency_map
end

#limit_map ⇒ Object (readonly)

Hash with table alias symbol keys and [limit, offset] values



2586
2587
2588
 
# File 'lib/sequel/model/associations.rb', line 2586

def limit_map
  @limit_map
end

#master ⇒ Object (readonly)

Hash with table alias symbol keys and callable values used to create model instances The table alias symbol for the primary model



2590
2591
2592
 
# File 'lib/sequel/model/associations.rb', line 2590

def master
  @master
end

#primary_keys ⇒ Object (readonly)

Hash with table alias symbol keys and primary key symbol values (or arrays of primary key symbols for composite key tables)



2594
2595
2596
 
# File 'lib/sequel/model/associations.rb', line 2594

def primary_keys
  @primary_keys
end

#reciprocal_map ⇒ Object (readonly)

Hash with table alias symbol keys and reciprocal association symbol values, used for setting reciprocals for one_to_many associations.



2598
2599
2600
 
# File 'lib/sequel/model/associations.rb', line 2598

def reciprocal_map
  @reciprocal_map
end

#records_map ⇒ Object (readonly)

Hash with table alias symbol keys and subhash values mapping primary key symbols (or array of symbols) to model instances. Used so that only a single model instance is created for each object.



2602
2603
2604
 
# File 'lib/sequel/model/associations.rb', line 2602

def records_map
  @records_map
end

#reflection_map ⇒ Object (readonly)

Hash with table alias symbol keys and AssociationReflection values



2605
2606
2607
 
# File 'lib/sequel/model/associations.rb', line 2605

def reflection_map
  @reflection_map
end

#row_procs ⇒ Object (readonly)

Hash with table alias symbol keys and callable values used to create model instances



2608
2609
2610
 
# File 'lib/sequel/model/associations.rb', line 2608

def row_procs
  @row_procs
end

#type_map ⇒ Object (readonly)

Hash with table alias symbol keys and true/false values, where true means the association represented by the table alias uses an array of values instead of a single value (i.e. true => *_many, false => *_to_one).



2613
2614
2615
 
# File 'lib/sequel/model/associations.rb', line 2613

def type_map
  @type_map
end

Instance Method Details

#load(hashes) ⇒ Object

Return an array of primary model instances with the associations cache prepopulated for all model objects (both primary and associated).



2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
 
# File 'lib/sequel/model/associations.rb', line 2718

def load(hashes)
  master = master()
      
  # Assign to local variables for speed increase
  rp = row_procs[master]
  rm = records_map[master]
  dm = dependency_map

  # This will hold the final record set that we will be replacing the object graph with.
  records = []

  hashes.each do |h|
    unless key = master_pk(h)
      key = hkey(master_hfor(h))
    end
    unless primary_record = rm[key]
      primary_record = rm[key] = rp.call(master_hfor(h))
      # Only add it to the list of records to return if it is a new record
      records.push(primary_record)
    end
    # Build all associations for the current object and it's dependencies
    _load(dm, primary_record, h)
  end
      
  # Remove duplicate records from all associations if this graph could possibly be a cartesian product
  # Run after_load procs if there are any
  post_process(records, dm) if @unique || !after_load_map.empty? || !limit_map.empty?

  records
end