[API] Omit X-Total{,-Pages} when count > 10k

Signed-off-by: 's avatarRémy Coutable <remy@rymai.me>
parent 7363428c
---
title: "[API] Omit `X-Total` and `X-Total-Pages` headers when items count is more than 10,000"
merge_request: 23931
author:
type: performance
module Kaminari
# Active Record specific page scope methods implementations
module ActiveRecordRelationMethodsWithLimit
MAX_COUNT_LIMIT = 10_000
# This is a modified version of
# https://github.com/kaminari/kaminari/blob/c5186f5d9b7f23299d115408e62047447fd3189d/kaminari-activerecord/lib/kaminari/activerecord/active_record_relation_methods.rb#L17-L41
# that limit the COUNT query to 10,000 to avoid query timeouts.
# rubocop: disable Gitlab/ModuleWithInstanceVariables
def total_count_with_limit(column_name = :all, _options = nil) #:nodoc:
return @total_count if defined?(@total_count) && @total_count
# There are some cases that total count can be deduced from loaded records
if loaded?
# Total count has to be 0 if loaded records are 0
return @total_count = 0 if (current_page == 1) && @records.empty?
# Total count is calculable at the last page
return @total_count = (current_page - 1) * limit_value + @records.length if @records.any? && (@records.length < limit_value)
end
# #count overrides the #select which could include generated columns referenced in #order, so skip #order here, where it's irrelevant to the result anyway
c = except(:offset, :limit, :order)
# Remove includes only if they are irrelevant
c = c.except(:includes) unless references_eager_loaded_tables?
# .group returns an OrderedHash that responds to #count
# The following line was modified from `c = c.count(:all)`
c = c.limit(MAX_COUNT_LIMIT + 1).count(column_name)
@total_count =
if c.is_a?(Hash) || c.is_a?(ActiveSupport::OrderedHash)
c.count
elsif c.respond_to? :count
c.count(column_name)
else
c
end
end
# rubocop: enable Gitlab/ModuleWithInstanceVariables
Kaminari::ActiveRecordRelationMethods.prepend(self)
end
end
......@@ -438,6 +438,14 @@ Additional pagination headers are also sent back.
| `X-Next-Page` | The index of the next page |
| `X-Prev-Page` | The index of the previous page |
CAUTION: **Caution:**
For performance reasons since
[GitLab 11.8][https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23931]
and **behind the `api_kaminari_count_with_limit`
[feature flag](../development/feature_flags.md)**, if the number of resources is
more than 10,000, the `X-Total` and `X-Total-Pages` headers as well as the
`rel="last"` `Link` are not present in the response headers.
## Namespaced path encoding
If using namespaced API calls, make sure that the `NAMESPACE/PROJECT_NAME` is
......
......@@ -178,15 +178,26 @@ module API
end
def paginate(relation)
relation = add_default_order(relation)
relation.page(params[:page]).per(params[:per_page]).tap do |data|
paginate_with_limit_optimization(add_default_order(relation)).tap do |data|
add_pagination_headers(data)
end
end
private
def paginate_with_limit_optimization(relation)
pagination_data = relation.page(params[:page]).per(params[:per_page])
return pagination_data unless pagination_data.is_a?(ActiveRecord::Relation)
return pagination_data unless Feature.enabled?(:api_kaminari_count_with_limit)
limited_total_count = pagination_data.total_count_with_limit
if limited_total_count > Kaminari::ActiveRecordRelationMethods::MAX_COUNT_LIMIT
pagination_data.without_count
else
pagination_data
end
end
# rubocop: disable CodeReuse/ActiveRecord
def add_default_order(relation)
if relation.is_a?(ActiveRecord::Relation) && relation.order_values.empty?
......
......@@ -237,26 +237,89 @@ describe API::Helpers::Pagination do
.and_return({ page: 1, per_page: 2 })
end
it 'returns appropriate amount of resources' do
expect(subject.paginate(resource).count).to eq 2
shared_examples 'response with pagination headers' do
it 'adds appropriate headers' do
expect_header('X-Total', '3')
expect_header('X-Total-Pages', '2')
expect_header('X-Per-Page', '2')
expect_header('X-Page', '1')
expect_header('X-Next-Page', '2')
expect_header('X-Prev-Page', '')
expect_header('Link', anything) do |_key, val|
expect(val).to include('rel="first"')
expect(val).to include('rel="last"')
expect(val).to include('rel="next"')
expect(val).not_to include('rel="prev"')
end
subject.paginate(resource)
end
end
it 'adds appropriate headers' do
expect_header('X-Total', '3')
expect_header('X-Total-Pages', '2')
expect_header('X-Per-Page', '2')
expect_header('X-Page', '1')
expect_header('X-Next-Page', '2')
expect_header('X-Prev-Page', '')
shared_examples 'paginated response' do
it 'returns appropriate amount of resources' do
expect(subject.paginate(resource).count).to eq 2
end
expect_header('Link', anything) do |_key, val|
expect(val).to include('rel="first"')
expect(val).to include('rel="last"')
expect(val).to include('rel="next"')
expect(val).not_to include('rel="prev"')
it 'executes only one SELECT COUNT query' do
expect { subject.paginate(resource) }.to make_queries_matching(/SELECT COUNT/, 1)
end
end
subject.paginate(resource)
context 'when the api_kaminari_count_with_limit feature flag is unset' do
it_behaves_like 'paginated response'
it_behaves_like 'response with pagination headers'
end
context 'when the api_kaminari_count_with_limit feature flag is disabled' do
before do
stub_feature_flags(api_kaminari_count_with_limit: false)
end
it_behaves_like 'paginated response'
it_behaves_like 'response with pagination headers'
end
context 'when the api_kaminari_count_with_limit feature flag is enabled' do
before do
stub_feature_flags(api_kaminari_count_with_limit: true)
end
context 'when resources count is less than MAX_COUNT_LIMIT' do
before do
stub_const("::Kaminari::ActiveRecordRelationMethods::MAX_COUNT_LIMIT", 4)
end
it_behaves_like 'paginated response'
it_behaves_like 'response with pagination headers'
end
context 'when resources count is more than MAX_COUNT_LIMIT' do
before do
stub_const("::Kaminari::ActiveRecordRelationMethods::MAX_COUNT_LIMIT", 2)
end
it_behaves_like 'paginated response'
it 'does not return the X-Total and X-Total-Pages headers' do
expect_no_header('X-Total')
expect_no_header('X-Total-Pages')
expect_header('X-Per-Page', '2')
expect_header('X-Page', '1')
expect_header('X-Next-Page', '2')
expect_header('X-Prev-Page', '')
expect_header('Link', anything) do |_key, val|
expect(val).to include('rel="first"')
expect(val).not_to include('rel="last"')
expect(val).to include('rel="next"')
expect(val).not_to include('rel="prev"')
end
subject.paginate(resource)
end
end
end
end
......@@ -348,6 +411,10 @@ describe API::Helpers::Pagination do
expect(subject).to receive(:header).with(*args, &block)
end
def expect_no_header(*args, &block)
expect(subject).not_to receive(:header).with(*args)
end
def expect_message(method)
expect(subject).to receive(method)
.at_least(:once).and_return(value)
......
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