Add keyset pagination for API calls.

Closes #45756.

1 files changed, 204 insertions, 8 deletions

diff --git a/spec/lib/api/helpers/pagination_spec.rb b/spec/lib/api/helpers/pagination_spec.rb
index a547988d631..c73c6023b60 100644
--- a/spec/lib/api/helpers/pagination_spec.rb
+++ b/spec/lib/api/helpers/pagination_spec.rb
@@ -7,7 +7,203 @@ describe API::Helpers::Pagination do
     Class.new.include(described_class).new
   end
 
-  describe '#paginate' do
+  describe '#paginate (keyset pagination)' do
+    let(:value) { spy('return value') }
+
+    before do
+      allow(value).to receive(:to_query).and_return(value)
+
+      allow(subject).to receive(:header).and_return(value)
+      allow(subject).to receive(:params).and_return(value)
+      allow(subject).to receive(:request).and_return(value)
+    end
+
+    context 'when resource can be paginated' do
+      let!(:projects) do
+        [
+          create(:project, name: 'One'),
+          create(:project, name: 'Two'),
+          create(:project, name: 'Three')
+        ].sort_by { |e| -e.id } # sort by id desc (this is the default sort order for the API)
+      end
+
+      describe 'first page' do
+        before do
+          allow(subject).to receive(:params)
+            .and_return({ pagination: 'keyset', per_page: 2 })
+        end
+
+        it 'returns appropriate amount of resources' do
+          expect(subject.paginate(resource).count).to eq 2
+        end
+
+        it 'returns the first two records (by id desc)' do
+          expect(subject.paginate(resource)).to eq(projects[0..1])
+        end
+
+        it 'adds appropriate headers' do
+          expect_header('X-Per-Page', '2')
+          expect_header('X-Next-Page', "#{value}?ks_prev_id=#{projects[1].id}&pagination=keyset&per_page=2")
+
+          expect_header('Link', anything) do |_key, val|
+            expect(val).to include('rel="next"')
+          end
+
+          subject.paginate(resource)
+        end
+      end
+
+      describe 'second page' do
+        before do
+          allow(subject).to receive(:params)
+            .and_return({ pagination: 'keyset', per_page: 2, ks_prev_id: projects[1].id })
+        end
+
+        it 'returns appropriate amount of resources' do
+          expect(subject.paginate(resource).count).to eq 1
+        end
+
+        it 'returns the third record' do
+          expect(subject.paginate(resource)).to eq(projects[2..2])
+        end
+
+        it 'adds appropriate headers' do
+          expect_header('X-Per-Page', '2')
+          expect_header('X-Next-Page', "#{value}?ks_prev_id=#{projects[2].id}&pagination=keyset&per_page=2")
+
+          expect_header('Link', anything) do |_key, val|
+            expect(val).to include('rel="next"')
+          end
+
+          subject.paginate(resource)
+        end
+      end
+
+      describe 'third page' do
+        before do
+          allow(subject).to receive(:params)
+            .and_return({ pagination: 'keyset', per_page: 2, ks_prev_id: projects[2].id })
+        end
+
+        it 'returns appropriate amount of resources' do
+          expect(subject.paginate(resource).count).to eq 0
+        end
+
+        it 'adds appropriate headers' do
+          expect_header('X-Per-Page', '2')
+          expect(subject).not_to receive(:header).with('Link')
+
+          subject.paginate(resource)
+        end
+      end
+
+      context 'if order' do
+        context 'is not present' do
+          before do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', per_page: 2 })
+          end
+
+          it 'is not present it adds default order(:id) desc' do
+            resource.order_values = []
+
+            paginated_relation = subject.paginate(resource)
+
+            expect(resource.order_values).to be_empty
+            expect(paginated_relation.order_values).to be_present
+            expect(paginated_relation.order_values.size).to eq(1)
+            expect(paginated_relation.order_values.first).to be_descending
+            expect(paginated_relation.order_values.first.expr.name).to eq :id
+          end
+        end
+
+        context 'is present' do
+          let(:resource) { Project.all.order(name: :desc) }
+          let!(:projects) do
+            [
+              create(:project, name: 'One'),
+              create(:project, name: 'Two'),
+              create(:project, name: 'Three'),
+              create(:project, name: 'Three'), # Note the duplicate name
+              create(:project, name: 'Four'),
+              create(:project, name: 'Five'),
+              create(:project, name: 'Six')
+            ]
+
+            # if we sort this by name descending, id descending, this yields:
+            # {
+            #   2 => "Two",
+            #   4 => "Three",
+            #   3 => "Three",
+            #   7 => "Six",
+            #   1 => "One",
+            #   5 => "Four",
+            #   6 => "Five"
+            # }
+            #
+            # (key is the id)
+          end
+
+          it 'it also orders by primary key' do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', per_page: 2 })
+            paginated_relation = subject.paginate(resource)
+
+            expect(paginated_relation.order_values).to be_present
+            expect(paginated_relation.order_values.size).to eq(2)
+            expect(paginated_relation.order_values.first).to be_descending
+            expect(paginated_relation.order_values.first.expr.name).to eq :name
+            expect(paginated_relation.order_values.second).to be_descending
+            expect(paginated_relation.order_values.second.expr.name).to eq :id
+          end
+
+          it 'it returns the right records (first page)' do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', per_page: 2 })
+            result = subject.paginate(resource)
+
+            expect(result.first).to eq(projects[1])
+            expect(result.second).to eq(projects[3])
+          end
+
+          it 'it returns the right records (second page)' do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', ks_prev_id: projects[3].id, ks_prev_name: projects[3].name, per_page: 2 })
+            result = subject.paginate(resource)
+
+            expect(result.first).to eq(projects[2])
+            expect(result.second).to eq(projects[6])
+          end
+
+          it 'it returns the right records (third page), note increased per_page' do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', ks_prev_id: projects[6].id, ks_prev_name: projects[6].name, per_page: 5 })
+            result = subject.paginate(resource)
+
+            expect(result.size).to eq(3)
+            expect(result.first).to eq(projects[0])
+            expect(result.second).to eq(projects[4])
+            expect(result.last).to eq(projects[5])
+          end
+
+          it 'it returns the right link to the next page' do
+            allow(subject).to receive(:params)
+              .and_return({ pagination: 'keyset', ks_prev_id: projects[3].id, ks_prev_name: projects[3].name, per_page: 2 })
+            expect_header('X-Per-Page', '2')
+            expect_header('X-Next-Page', "#{value}?ks_prev_id=#{projects[6].id}&ks_prev_name=#{projects[6].name}&pagination=keyset&per_page=2")
+
+            expect_header('Link', anything) do |_key, val|
+              expect(val).to include('rel="next"')
+            end
+
+            subject.paginate(resource)
+          end
+        end
+      end
+    end
+  end
+
+  describe '#paginate (default offset-based pagination)' do
     let(:value) { spy('return value') }
 
     before do
@@ -146,14 +342,14 @@ describe API::Helpers::Pagination do
         end
       end
     end
+  end
 
-    def expect_header(*args, &block)
-      expect(subject).to receive(:header).with(*args, &block)
-    end
+  def expect_header(*args, &block)
+    expect(subject).to receive(:header).with(*args, &block)
+  end
 
-    def expect_message(method)
-      expect(subject).to receive(method)
-        .at_least(:once).and_return(value)
-    end
+  def expect_message(method)
+    expect(subject).to receive(method)
+      .at_least(:once).and_return(value)
   end
 end