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module ActiveRecord
module Associations
class Preloader
class Association #:nodoc:
attr_reader :owners, :reflection, :preload_scope, :model, :klass
attr_reader :preloaded_records
def initialize(klass, owners, reflection, preload_scope)
@klass = klass
@owners = owners
@reflection = reflection
@preload_scope = preload_scope
@model = owners.first && owners.first.class
@scope = nil
@preloaded_records = []
end
def run(preloader)
preload(preloader)
end
def preload(preloader)
raise NotImplementedError
end
def scope
@scope ||= build_scope
end
def records_for(ids)
query_scope(ids)
end
def query_scope(ids)
scope.where(association_key_name => ids)
end
def table
klass.arel_table
end
# The name of the key on the associated records
def association_key_name
raise NotImplementedError
end
# This is overridden by HABTM as the condition should be on the foreign_key column in
# the join table
def association_key
klass.arel_attribute(association_key_name, table)
end
# The name of the key on the model which declares the association
def owner_key_name
raise NotImplementedError
end
def options
reflection.options
end
private
def associated_records_by_owner(preloader)
records = load_records
owners.each_with_object({}) do |owner, result|
result[owner] = records[convert_key(owner[owner_key_name])] || []
end
end
def owner_keys
unless defined?(@owner_keys)
@owner_keys = owners.map do |owner|
owner[owner_key_name]
end
@owner_keys.uniq!
@owner_keys.compact!
end
@owner_keys
end
def key_conversion_required?
@key_conversion_required ||= association_key_type != owner_key_type
end
def convert_key(key)
if key_conversion_required?
key.to_s
else
key
end
end
def association_key_type
@klass.type_for_attribute(association_key_name.to_s).type
end
def owner_key_type
@model.type_for_attribute(owner_key_name.to_s).type
end
def load_records
return {} if owner_keys.empty?
# Some databases impose a limit on the number of ids in a list (in Oracle it's 1000)
# Make several smaller queries if necessary or make one query if the adapter supports it
slices = owner_keys.each_slice(klass.connection.in_clause_length || owner_keys.size)
@preloaded_records = slices.flat_map do |slice|
records_for(slice)
end
@preloaded_records.group_by do |record|
convert_key(record[association_key_name])
end
end
def reflection_scope
@reflection_scope ||= reflection.scope_for(klass)
end
def build_scope
scope = klass.unscoped
values = reflection_scope.values
preload_values = preload_scope.values
scope.where_clause = reflection_scope.where_clause + preload_scope.where_clause
scope.references_values = Array(values[:references]) + Array(preload_values[:references])
if preload_values[:select] || values[:select]
scope._select!(preload_values[:select] || values[:select])
end
scope.includes! preload_values[:includes] || values[:includes]
if preload_scope.joins_values.any?
scope.joins!(preload_scope.joins_values)
else
scope.joins!(reflection_scope.joins_values)
end
if order_values = preload_values[:order] || values[:order]
scope.order!(order_values)
end
if preload_values[:reordering] || values[:reordering]
scope.reordering_value = true
end
if preload_values[:readonly] || values[:readonly]
scope.readonly!
end
if options[:as]
scope.where!(klass.table_name => { reflection.type => model.base_class.sti_name })
end
scope.unscope_values = Array(values[:unscope]) + Array(preload_values[:unscope])
klass.default_scoped.merge(scope)
end
end
end
end
end
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