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|
# frozen_string_literal: true
module Gitlab
module ImportExport
module Json
class StreamingSerializer
include Gitlab::ImportExport::CommandLineUtil
BATCH_SIZE = 2
def self.batch_size(exportable)
BATCH_SIZE
end
class Raw < String
def to_json(*_args)
to_s
end
end
def initialize(exportable, relations_schema, json_writer, exportable_path:)
@exportable = exportable
@exportable_path = exportable_path
@relations_schema = relations_schema
@json_writer = json_writer
end
def execute
read_from_replica_if_available do
serialize_root
includes.each do |relation_definition|
serialize_relation(relation_definition)
end
end
end
def serialize_root(exportable_path = @exportable_path)
attributes = exportable.as_json(
relations_schema.merge(include: nil, preloads: nil))
json_writer.write_attributes(exportable_path, attributes)
end
def serialize_relation(definition)
raise ArgumentError, 'definition needs to be Hash' unless definition.is_a?(Hash)
raise ArgumentError, 'definition needs to have exactly one Hash element' unless definition.one?
key, options = definition.first
record = exportable.public_send(key) # rubocop: disable GitlabSecurity/PublicSend
if record.is_a?(ActiveRecord::Relation)
serialize_many_relations(key, record, options)
elsif record.respond_to?(:each) # this is to support `project_members` that return an Array
serialize_many_each(key, record, options)
else
serialize_single_relation(key, record, options)
end
end
private
attr_reader :json_writer, :relations_schema, :exportable
def serialize_many_relations(key, records, options)
enumerator = Enumerator.new do |items|
key_preloads = preloads&.dig(key)
batch(records, key) do |batch|
batch = batch.preload(key_preloads) if key_preloads
batch.each do |record|
items << Raw.new(record.to_json(options))
end
end
end
json_writer.write_relation_array(@exportable_path, key, enumerator)
end
def batch(relation, key)
opts = { of: batch_size }
order_by = reorders(relation, key)
# we need to sort issues by non primary key column(relative_position)
# and `in_batches` does not support that
if order_by
scope = relation.reorder(order_by)
Gitlab::Pagination::Keyset::Iterator.new(scope: scope, use_union_optimization: true).each_batch(**opts) do |batch|
yield batch
end
else
relation.in_batches(**opts) do |batch| # rubocop:disable Cop/InBatches
# order each batch by its primary key to ensure
# consistent and predictable ordering of each exported relation
# as additional `WHERE` clauses can impact the order in which data is being
# returned by database when no `ORDER` is specified
yield batch.reorder(batch.klass.primary_key)
end
end
end
def serialize_many_each(key, records, options)
enumerator = Enumerator.new do |items|
records.each do |record|
items << Raw.new(record.to_json(options))
end
end
json_writer.write_relation_array(@exportable_path, key, enumerator)
end
def serialize_single_relation(key, record, options)
json = Raw.new(record.to_json(options))
json_writer.write_relation(@exportable_path, key, json)
end
def includes
relations_schema[:include]
end
def preloads
relations_schema[:preload]
end
def batch_size
@batch_size ||= self.class.batch_size(@exportable)
end
def reorders(relation, key)
export_reorder = relations_schema[:export_reorder]&.dig(key)
return unless export_reorder
custom_reorder(relation.klass, export_reorder)
end
def custom_reorder(klass, order_by)
arel_table = klass.arel_table
column = order_by[:column] || klass.primary_key
direction = order_by[:direction] || :asc
nulls_position = order_by[:nulls_position] || :nulls_last
arel_order_classes = ::Gitlab::Pagination::Keyset::ColumnOrderDefinition::AREL_ORDER_CLASSES.invert
reverse_direction = ::Gitlab::Pagination::Keyset::ColumnOrderDefinition::REVERSED_ORDER_DIRECTIONS[direction]
reverse_nulls_position = ::Gitlab::Pagination::Keyset::ColumnOrderDefinition::REVERSED_NULL_POSITIONS[nulls_position]
order_expression = ::Gitlab::Database.nulls_order(column, direction, nulls_position)
reverse_order_expression = ::Gitlab::Database.nulls_order(column, reverse_direction, reverse_nulls_position)
::Gitlab::Pagination::Keyset::Order.build([
::Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
attribute_name: column,
column_expression: arel_table[column],
order_expression: order_expression,
reversed_order_expression: reverse_order_expression,
order_direction: direction,
nullable: nulls_position,
distinct: false
),
::Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
attribute_name: klass.primary_key,
order_expression: arel_order_classes[direction].new(arel_table[klass.primary_key.to_sym])
)
])
end
def read_from_replica_if_available(&block)
::Gitlab::Database::LoadBalancing::Session.current.use_replicas_for_read_queries(&block)
end
end
end
end
end
|
