139 lines
4.7 KiB
Ruby
139 lines
4.7 KiB
Ruby
# frozen_string_literal: true
|
|
|
|
# Keyset::Connection provides cursor based pagination, to avoid using OFFSET.
|
|
# It basically sorts / filters using WHERE sorting_value > cursor.
|
|
# We do this for performance reasons (https://gitlab.com/gitlab-org/gitlab-foss/issues/45756),
|
|
# as well as for having stable pagination
|
|
# https://graphql-ruby.org/pro/cursors.html#whats-the-difference
|
|
# https://coderwall.com/p/lkcaag/pagination-you-re-probably-doing-it-wrong
|
|
#
|
|
# It currently supports sorting on two columns, but the last column must
|
|
# be the primary key. If it's not already included, an order on the
|
|
# primary key will be added automatically, like `order(id: :desc)`
|
|
#
|
|
# Issue.order(created_at: :asc).order(:id)
|
|
# Issue.order(due_date: :asc)
|
|
#
|
|
# You can also use `Gitlab::Database.nulls_last_order`:
|
|
#
|
|
# Issue.reorder(::Gitlab::Database.nulls_last_order('due_date', 'DESC'))
|
|
#
|
|
# It will tolerate non-attribute ordering, but only attributes determine the cursor.
|
|
# For example, this is legitimate:
|
|
#
|
|
# Issue.order('issues.due_date IS NULL').order(due_date: :asc).order(:id)
|
|
#
|
|
# but anything more complex has a chance of not working.
|
|
#
|
|
module Gitlab
|
|
module Graphql
|
|
module Pagination
|
|
module Keyset
|
|
class Connection < GraphQL::Pagination::ActiveRecordRelationConnection
|
|
include Gitlab::Utils::StrongMemoize
|
|
|
|
def cursor_for(node)
|
|
encoded_json_from_ordering(node)
|
|
end
|
|
|
|
def sliced_nodes
|
|
@sliced_nodes ||=
|
|
begin
|
|
OrderInfo.validate_ordering(ordered_items, order_list)
|
|
|
|
sliced = ordered_items
|
|
sliced = slice_nodes(sliced, before, :before) if before.present?
|
|
sliced = slice_nodes(sliced, after, :after) if after.present?
|
|
|
|
sliced
|
|
end
|
|
end
|
|
|
|
def nodes
|
|
# These are the nodes that will be loaded into memory for rendering
|
|
# So we're ok loading them into memory here as that's bound to happen
|
|
# anyway. Having them ready means we can modify the result while
|
|
# rendering the fields.
|
|
@nodes ||= load_paged_nodes.to_a
|
|
end
|
|
|
|
private
|
|
|
|
def load_paged_nodes
|
|
if first && last
|
|
raise Gitlab::Graphql::Errors::ArgumentError.new("Can only provide either `first` or `last`, not both")
|
|
end
|
|
|
|
if last
|
|
sliced_nodes.last(limit_value)
|
|
else
|
|
sliced_nodes.limit(limit_value) # rubocop: disable CodeReuse/ActiveRecord
|
|
end
|
|
end
|
|
|
|
# rubocop: disable CodeReuse/ActiveRecord
|
|
def slice_nodes(sliced, encoded_cursor, before_or_after)
|
|
decoded_cursor = ordering_from_encoded_json(encoded_cursor)
|
|
builder = QueryBuilder.new(arel_table, order_list, decoded_cursor, before_or_after)
|
|
ordering = builder.conditions
|
|
|
|
sliced.where(*ordering).where.not(id: decoded_cursor['id'])
|
|
end
|
|
# rubocop: enable CodeReuse/ActiveRecord
|
|
|
|
def limit_value
|
|
@limit_value ||= [first, last, max_page_size].compact.min
|
|
end
|
|
|
|
def ordered_items
|
|
strong_memoize(:ordered_items) do
|
|
unless items.primary_key.present?
|
|
raise ArgumentError.new('Relation must have a primary key')
|
|
end
|
|
|
|
list = OrderInfo.build_order_list(items)
|
|
|
|
# ensure there is a primary key ordering
|
|
if list&.last&.attribute_name != items.primary_key
|
|
items.order(arel_table[items.primary_key].desc) # rubocop: disable CodeReuse/ActiveRecord
|
|
else
|
|
items
|
|
end
|
|
end
|
|
end
|
|
|
|
def order_list
|
|
strong_memoize(:order_list) do
|
|
OrderInfo.build_order_list(ordered_items)
|
|
end
|
|
end
|
|
|
|
def arel_table
|
|
items.arel_table
|
|
end
|
|
|
|
# Storing the current order values in the cursor allows us to
|
|
# make an intelligent decision on handling NULL values.
|
|
# Otherwise we would either need to fetch the record first,
|
|
# or fetch it in the SQL, significantly complicating it.
|
|
def encoded_json_from_ordering(node)
|
|
ordering = { 'id' => node[:id].to_s }
|
|
|
|
order_list.each do |field|
|
|
field_name = field.attribute_name
|
|
ordering[field_name] = node[field_name].to_s
|
|
end
|
|
|
|
encode(ordering.to_json)
|
|
end
|
|
|
|
def ordering_from_encoded_json(cursor)
|
|
JSON.parse(decode(cursor))
|
|
rescue JSON::ParserError
|
|
raise Gitlab::Graphql::Errors::ArgumentError, "Please provide a valid cursor"
|
|
end
|
|
end
|
|
end
|
|
end
|
|
end
|
|
end
|