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.



2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
 
# File 'lib/sequel/model/associations.rb', line 2927

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



2884
2885
2886
 
# File 'lib/sequel/model/associations.rb', line 2884

def after_load_map
  @after_load_map
end

#alias_map ⇒ Object (readonly)

Hash with table alias symbol keys and association name values



2887
2888
2889
 
# File 'lib/sequel/model/associations.rb', line 2887

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



2891
2892
2893
 
# File 'lib/sequel/model/associations.rb', line 2891

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.



2894
2895
2896
 
# File 'lib/sequel/model/associations.rb', line 2894

def dependency_map
  @dependency_map
end

#limit_map ⇒ Object (readonly)

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



2897
2898
2899
 
# File 'lib/sequel/model/associations.rb', line 2897

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



2901
2902
2903
 
# File 'lib/sequel/model/associations.rb', line 2901

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)



2905
2906
2907
 
# File 'lib/sequel/model/associations.rb', line 2905

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.



2909
2910
2911
 
# File 'lib/sequel/model/associations.rb', line 2909

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.



2913
2914
2915
 
# File 'lib/sequel/model/associations.rb', line 2913

def records_map
  @records_map
end

#reflection_map ⇒ Object (readonly)

Hash with table alias symbol keys and AssociationReflection values



2916
2917
2918
 
# File 'lib/sequel/model/associations.rb', line 2916

def reflection_map
  @reflection_map
end

#row_procs ⇒ Object (readonly)

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



2919
2920
2921
 
# File 'lib/sequel/model/associations.rb', line 2919

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).



2924
2925
2926
 
# File 'lib/sequel/model/associations.rb', line 2924

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).



3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
 
# File 'lib/sequel/model/associations.rb', line 3029

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