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.



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# File 'lib/sequel/model/associations.rb', line 1719

def initialize(dataset)
  opts = dataset.opts
  eager_graph = opts[:eager_graph]
  @master =  eager_graph[:master]
  requirements = eager_graph[:requirements]
  alias_map = @alias_map = eager_graph[:alias_association_name_map]
  type_map = @type_map = eager_graph[:alias_association_type_map]
  reciprocal_map = @reciprocal_map = eager_graph[:reciprocals]
  @unique = eager_graph[:cartesian_product_number] > 1
      
  # 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

#alias_map ⇒ Object (readonly)

Hash with table alias symbol keys and association name values



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# File 'lib/sequel/model/associations.rb', line 1686

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



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# File 'lib/sequel/model/associations.rb', line 1690

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.



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# File 'lib/sequel/model/associations.rb', line 1693

def dependency_map
  @dependency_map
end

#master ⇒ Object (readonly)

The table alias symbol for the primary model



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# File 'lib/sequel/model/associations.rb', line 1696

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)



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# File 'lib/sequel/model/associations.rb', line 1700

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.



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# File 'lib/sequel/model/associations.rb', line 1704

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.



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# File 'lib/sequel/model/associations.rb', line 1708

def records_map
  @records_map
end

#row_procs ⇒ Object (readonly)

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



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# File 'lib/sequel/model/associations.rb', line 1711

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).



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# File 'lib/sequel/model/associations.rb', line 1716

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).



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# File 'lib/sequel/model/associations.rb', line 1808

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
  unique(records, dm) if @unique
  
  records
end