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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
@owners_by_key = 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.in(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
table[association_key_name]
end
# The name of the key on the model which declares the association
def owner_key_name
raise NotImplementedError
end
def owners_by_key
@owners_by_key ||= owners.group_by do |owner|
owner[owner_key_name]
end
end
def options
reflection.options
end
private
def associated_records_by_owner(preloader)
owners_map = owners_by_key
owner_keys = owners_map.keys.compact
# Each record may have multiple owners, and vice-versa
records_by_owner = owners.each_with_object({}) do |owner,h|
h[owner] = []
end
if owner_keys.any?
# 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
sliced = owner_keys.each_slice(klass.connection.in_clause_length || owner_keys.size)
records = load_slices sliced
records.each do |record, owner_key|
owners_map[owner_key].each do |owner|
records_by_owner[owner] << record
end
end
end
records_by_owner
end
def load_slices(slices)
@preloaded_records = slices.flat_map { |slice|
records_for(slice)
}
@preloaded_records.map { |record|
[record, record[association_key_name]]
}
end
def reflection_scope
@reflection_scope ||= reflection.scope ? klass.unscoped.instance_exec(nil, &reflection.scope) : klass.unscoped
end
def build_scope
scope = klass.unscoped
values = reflection_scope.values
preload_values = preload_scope.values
scope.where_values = Array(values[:where]) + Array(preload_values[:where])
scope.references_values = Array(values[:references]) + Array(preload_values[:references])
scope.select! preload_values[:select] || values[:select] || table[Arel.star]
scope.includes! preload_values[:includes] || values[:includes]
if preload_values.key? :order
scope.order! preload_values[:order]
else
if values.key? :order
scope.order! values[:order]
end
end
if options[:as]
scope.where!(klass.table_name => { reflection.type => model.base_class.sti_name })
end
klass.default_scoped.merge(scope)
end
end
end
end
end
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