Module: IdentityCache::QueryAPI::ClassMethods

Defined in:
lib/identity_cache/query_api.rb

Instance Method Summary collapse

Instance Method Details

#all_cached_associations ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 100

def all_cached_associations
  (cached_has_manys || {}).merge(cached_has_ones || {}).merge(cached_belongs_tos || {})
end

#all_cached_associations_needing_population ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 104

def all_cached_associations_needing_population
  all_cached_associations.select do |cached_association, options|
    options[:population_method_name].present? # non-embedded belongs_to associations don't need population
  end
end

#cache_fetch_includes(additions = {}) ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 110

def cache_fetch_includes(additions = {})
  additions = hashify_includes_structure(additions)
  embedded_associations = all_cached_associations.select { |name, options| options[:embed] }

  associations_for_identity_cache = embedded_associations.map do |child_association, options|
    child_class = reflect_on_association(child_association).try(:klass)

    child_includes = additions.delete(child_association)

    if child_class.respond_to?(:cache_fetch_includes)
      child_includes = child_class.cache_fetch_includes(child_includes)
    end

    if child_includes.blank?
      child_association
    else
      { child_association => child_includes }
    end
  end

  associations_for_identity_cache.push(additions) if additions.keys.size > 0
  associations_for_identity_cache.compact
end

#exists_with_identity_cache?(id) ⇒ Boolean

Similar to ActiveRecord::Base#exists? will return true if the id can be found in the cache or in the DB.

Returns:

Raises:



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# File 'lib/identity_cache/query_api.rb', line 18

def exists_with_identity_cache?(id)
  raise NotImplementedError, "exists_with_identity_cache? needs the primary index enabled" unless primary_cache_index_enabled
  !!fetch_by_id(id)
end

#fetch(id) ⇒ Object

Default fetcher added to the model on inclusion, it behaves like ActiveRecord::Base.find, will raise ActiveRecord::RecordNotFound exception if id is not in the cache or the db.



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# File 'lib/identity_cache/query_api.rb', line 43

def fetch(id)
  fetch_by_id(id) or raise(ActiveRecord::RecordNotFound, "Couldn't find #{self.class.name} with ID=#{id}")
end

#fetch_by_id(id) ⇒ Object

Default fetcher added to the model on inclusion, it behaves like ActiveRecord::Base.find_by_id

Raises:



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# File 'lib/identity_cache/query_api.rb', line 25

def fetch_by_id(id)
  raise NotImplementedError, "fetching needs the primary index enabled" unless primary_cache_index_enabled
  if IdentityCache.should_cache?

    require_if_necessary do
      object = IdentityCache.fetch(rails_cache_key(id)){ resolve_cache_miss(id) }
      IdentityCache.logger.error "[IDC id mismatch] fetch_by_id_requested=#{id} fetch_by_id_got=#{object.id} for #{object.inspect[(0..100)]} " if object && object.id != id.to_i
      object
    end

  else
    self.find_by_id(id)
  end
end

#fetch_multi(*ids) ⇒ Object

Default fetcher added to the model on inclusion, if behaves like ActiveRecord::Base.find_all_by_id

Raises:



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# File 'lib/identity_cache/query_api.rb', line 49

def fetch_multi(*ids)
  raise NotImplementedError, "fetching needs the primary index enabled" unless primary_cache_index_enabled
  options = ids.extract_options!
  if IdentityCache.should_cache?

    require_if_necessary do
      cache_keys = ids.map {|id| rails_cache_key(id) }
      key_to_id_map = Hash[ cache_keys.zip(ids) ]

      objects_by_key = IdentityCache.fetch_multi(*cache_keys) do |unresolved_keys|
        ids = unresolved_keys.map {|key| key_to_id_map[key] }
        records = find_batch(ids, options)
        records.compact.each(&:populate_association_caches)
        records
      end

      records = cache_keys.map {|key| objects_by_key[key] }.compact
      prefetch_associations(options[:includes], records) if options[:includes]

      records
    end

  else
    find_batch(ids, options)
  end
end

#find_batch(ids, options = {}) ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 134

def find_batch(ids, options = {})
  @id_column ||= columns.detect {|c| c.name == "id"}
  ids = ids.map{ |id| @id_column.type_cast(id) }
  records = where('id IN (?)', ids).includes(cache_fetch_includes(options[:includes])).all
  records_by_id = records.index_by(&:id)
  records = ids.map{ |id| records_by_id[id] }
  mismatching_ids = records.compact.map(&:id) - ids
  IdentityCache.logger.error "[IDC id mismatch] fetch_batch_requested=#{ids.inspect} fetch_batch_got=#{mismatchig_ids.inspect} mismatching ids "  unless mismatching_ids.empty?
  records
end

#hashify_includes_structure(structure) ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 212

def hashify_includes_structure(structure)
  case structure
  when nil
    {}
  when Symbol
    {structure => []}
  when Hash
    structure.clone
  when Array
    structure.each_with_object({}) do |member, hash|
      case member
      when Hash
        hash.merge!(member)
      when Symbol
        hash[member] = []
      end
    end
  end
end

#prefetch_associations(associations, records) ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 145

def prefetch_associations(associations, records)
  associations = hashify_includes_structure(associations)

  associations.each do |association, sub_associations|
    case
    when details = cached_has_manys[association]

      if details[:embed]
        child_records = records.map(&details[:cached_accessor_name].to_sym).flatten
      else
        ids_to_parent_record = records.each_with_object({}) do |record, hash|
          child_ids = record.send(details[:cached_ids_name])
          child_ids.each do |child_id|
            hash[child_id] = record
          end
        end

        parent_record_to_child_records = Hash.new { |h, k| h[k] = [] }
        child_records = details[:association_class].fetch_multi(*ids_to_parent_record.keys)
        child_records.each do |child_record|
          parent_record = ids_to_parent_record[child_record.id]
          parent_record_to_child_records[parent_record] << child_record
        end

        parent_record_to_child_records.each do |parent_record, child_records|
          parent_record.send(details[:prepopulate_method_name], child_records)
        end
      end

      next_level_records = child_records

    when details = cached_belongs_tos[association]
      if details[:embed]
        raise ArgumentError.new("Embedded belongs_to associations do not support prefetching yet.")
      else
        ids_to_child_record = records.each_with_object({}) do |child_record, hash|
          parent_id = child_record.send(details[:foreign_key])
          hash[parent_id] = child_record if parent_id.present?
        end
        parent_records = details[:association_class].fetch_multi(*ids_to_child_record.keys)
        parent_records.each do |parent_record|
          child_record = ids_to_child_record[parent_record.id]
          child_record.send(details[:prepopulate_method_name], parent_record)
        end
      end

      next_level_records = parent_records

    when details = cached_has_ones[association]
      if details[:embed]
        parent_records = records.map(&details[:cached_accessor_name].to_sym)
      else
        raise ArgumentError.new("Non-embedded has_one associations do not support prefetching yet.")
      end

      next_level_records = parent_records

    else
      raise ArgumentError.new("Unknown cached association #{association} listed for prefetching")
    end

    if details && details[:association_class].respond_to?(:prefetch_associations)
      details[:association_class].prefetch_associations(sub_associations, next_level_records)
    end
  end
end

#require_if_necessary ⇒ Object

:nodoc:



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# File 'lib/identity_cache/query_api.rb', line 76

def require_if_necessary #:nodoc:
  # mem_cache_store returns raw value if unmarshal fails
  rval = yield
  case rval
  when String
    rval = Marshal.load(rval)
  when Array
    rval.map!{ |v| v.kind_of?(String) ? Marshal.load(v) : v }
  end
  rval
rescue ArgumentError => e
  if e.message =~ /undefined [\w\/]+ (\w+)/
    ok = Kernel.const_get($1) rescue nil
    retry if ok
  end
  raise
end

#resolve_cache_miss(id) ⇒ Object 



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# File 'lib/identity_cache/query_api.rb', line 94

def resolve_cache_miss(id)
  self.find_by_id(id, :include => cache_fetch_includes).tap do |object|
    object.try(:populate_association_caches)
  end
end