Merge pull request #2 from DmitryTsepelev/keyset-connections

Keyset connections

README.md

@@ -37,6 +37,28 @@ Records are sorted by model's primary key by default. You can change this behavi
 GraphQL::Connections::Stable.new(Message.all, primary_key: :created_at)
 ```
 
+In case when you want records to be sorted by more than one field (i.e., _keyset pagination_), you can use `keys` param:
+
+```ruby
+GraphQL::Connections::Stable.new(Message.all, keys: %w[name id])
+```
+
+When you pass only one key, a primary key will be added as a second one:
+
+```ruby
+GraphQL::Connections::Stable.new(Message.all, keys: [:name])
+```
+
+**NOTE:** Currently we support maximum two keys in the keyset.
+
+Also, you can pass the `:desc` option to reverse the relation:
+
+```ruby
+GraphQL::Connections::Stable.new(Message.all, keys: %w[name id], desc: true)
+```
+
+**NOTE:** `:desc` option is not implemented for stable connections with `:primary_key` passed; if you need it—use keyset pagination or implement `:desc` option for us 🙂.
+
 Also, you can disable opaque cursors by setting `opaque_cursor` param:
 
 ```ruby
@@ -53,7 +75,7 @@ class ApplicationSchema < GraphQL::Schema
 end
 ```
 
-**NOTE:** Don't use stable connections for relations whose ordering is too complicated for cursor generation. 
+**NOTE:** Don't use stable connections for relations whose ordering is too complicated for cursor generation.
 
 ## Development
 

lib/graphql/connections.rb

@@ -9,3 +9,10 @@ module Connections
 end
 
 require "graphql/connections/stable"
+
+require "graphql/connections/base"
+require "graphql/connections/key_asc"
+
+require "graphql/connections/keyset/base"
+require "graphql/connections/keyset/asc"
+require "graphql/connections/keyset/desc"

lib/graphql/connections/base.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module GraphQL
+  module Connections
+    # Base class for pagination implementations
+    class Base < ::GraphQL::Pagination::Connection
+      attr_reader :opaque_cursor
+
+      delegate :arel_table, to: :items
+
+      def initialize(*args, opaque_cursor: true, **kwargs)
+        @opaque_cursor = opaque_cursor
+
+        super(*args, **kwargs)
+      end
+
+      def primary_key
+        @primary_key ||= items.model.primary_key
+      end
+
+      def nodes
+        @nodes ||= limited_relation
+      end
+
+      def has_previous_page # rubocop:disable Naming/PredicateName
+        raise NotImplementedError
+      end
+
+      def has_next_page # rubocop:disable Naming/PredicateName
+        raise NotImplementedError
+      end
+
+      def cursor_for(item)
+        raise NotImplementedError
+      end
+
+      private
+
+      def serialize(cursor)
+        case cursor
+        when Time, DateTime, Date
+          cursor.iso8601
+        else
+          cursor.to_s
+        end
+      end
+
+      def limited_relation
+        raise NotImplementedError
+      end
+
+      def sliced_relation
+        raise NotImplementedError
+      end
+
+      def after_cursor
+        @after_cursor ||= opaque_cursor ? decode(after) : after
+      end
+
+      def before_cursor
+        @before_cursor ||= opaque_cursor ? decode(before) : before
+      end
+    end
+  end
+end

lib/graphql/connections/key_asc.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module GraphQL
+  module Connections
+    # Implements pagination by one field with asc order
+    class KeyAsc < ::GraphQL::Connections::Base
+      def initialize(*args, primary_key: nil, **kwargs)
+        @primary_key = primary_key
+
+        super(*args, **kwargs)
+      end
+
+      def has_previous_page # rubocop:disable Naming/PredicateName, Metrics/AbcSize
+        if last
+          nodes.any? && items.where(arel_table[primary_key].lt(nodes.first[primary_key])).exists?
+        elsif after
+          items.where(arel_table[primary_key].lteq(after_cursor)).exists?
+        else
+          false
+        end
+      end
+
+      def has_next_page # rubocop:disable Naming/PredicateName, Metrics/AbcSize
+        if first
+          nodes.any? && items.where(arel_table[primary_key].gt(nodes.last[primary_key])).exists?
+        elsif before
+          items.where(arel_table[primary_key].gteq(before_cursor)).exists?
+        else
+          false
+        end
+      end
+
+      def cursor_for(item)
+        cursor = serialize(item[primary_key])
+        cursor = encode(cursor) if opaque_cursor
+        cursor
+      end
+
+      private
+
+      def limited_relation # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
+        scope = sliced_relation
+        nodes = []
+
+        if first
+          nodes |= scope
+            .reorder(arel_table[primary_key].asc)
+            .limit(first)
+            .to_a
+        end
+
+        if last
+          nodes |= scope
+            .reorder(arel_table[primary_key].desc)
+            .limit(last)
+            .to_a.reverse!
+        end
+
+        nodes
+      end
+
+      def sliced_relation # rubocop:disable Metrics/AbcSize
+        items
+          .yield_self { |s| after ? s.where(arel_table[primary_key].gt(after_cursor)) : s }
+          .yield_self { |s| before ? s.where(arel_table[primary_key].lt(before_cursor)) : s }
+      end
+    end
+  end
+end

lib/graphql/connections/keyset/asc.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+module GraphQL
+  module Connections
+    module Keyset
+      # Implements keyset pagination by two fields with asc order
+      class Asc < ::GraphQL::Connections::Keyset::Base
+        # rubocop:disable Naming/PredicateName, Metrics/AbcSize, Metrics/MethodLength
+        def has_previous_page
+          if last
+            nodes.any? &&
+              items.where(arel_table[field_key].eq(nodes.first[field_key]))
+                .where(arel_table[primary_key].lt(nodes.first[primary_key]))
+                .or(items.where(arel_table[field_key].lt(nodes.first[field_key])))
+                .exists?
+          elsif after
+            items
+              .where(arel_table[field_key].lt(after_cursor_date))
+              .or(
+                items.where(arel_table[field_key].eq(after_cursor_date))
+                  .where(arel_table[primary_key].lt(after_cursor_primary_key))
+              ).exists?
+          else
+            false
+          end
+        end
+
+        def has_next_page
+          if first
+            nodes.any? &&
+              items.where(arel_table[field_key].eq(nodes.last[field_key]))
+                .where(arel_table[primary_key].gt(nodes.last[primary_key]))
+                .or(items.where(arel_table[field_key].gt(nodes.last[field_key])))
+                .exists?
+          elsif before
+            items
+              .where(arel_table[field_key].gt(before_cursor_date))
+              .or(
+                items.where(arel_table[field_key].eq(before_cursor_date))
+                  .where(arel_table[primary_key].gt(before_cursor_primary_key))
+              ).exists?
+          else
+            false
+          end
+        end
+        # rubocop:enable Naming/PredicateName, Metrics/AbcSize, Metrics/MethodLength
+
+        private
+
+        def limited_relation # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
+          scope = sliced_relation
+          nodes = []
+
+          if first
+            nodes |= scope
+              .reorder(arel_table[field_key].asc, arel_table[primary_key].asc)
+              .limit(first).to_a
+          end
+
+          if last
+            nodes |= scope
+              .reorder(arel_table[field_key].desc, arel_table[primary_key].desc)
+              .limit(last).to_a.reverse!
+          end
+
+          nodes
+        end
+
+        def sliced_relation_after(relation) # rubocop:disable Metrics/AbcSize
+          relation
+            .where(arel_table[field_key].eq(after_cursor_date))
+            .where(arel_table[primary_key].gt(after_cursor_primary_key))
+            .or(relation.where(arel_table[field_key].gt(after_cursor_date)))
+        end
+
+        def sliced_relation_before(relation) # rubocop:disable Metrics/AbcSize
+          relation
+            .where(arel_table[field_key].eq(before_cursor_date))
+            .where(arel_table[primary_key].lt(before_cursor_primary_key))
+            .or(relation.where(arel_table[field_key].lt(before_cursor_date)))
+        end
+      end
+    end
+  end
+end

lib/graphql/connections/keyset/base.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+module GraphQL
+  module Connections
+    module Keyset
+      # Base class for keyset pagination implementations
+      class Base < ::GraphQL::Connections::Base
+        attr_reader :field_key
+
+        SEPARATOR = "/"
+
+        def initialize(*args, keys:, separator: SEPARATOR, **kwargs)
+          @field_key, @primary_key = keys
+          @separator = separator
+
+          super(*args, **kwargs)
+        end
+
+        def cursor_for(item)
+          cursor = [item[field_key], item[primary_key]].map { |value| serialize(value) }.join(@separator)
+          cursor = encode(cursor) if opaque_cursor
+          cursor
+        end
+
+        private
+
+        def sliced_relation
+          items
+            .yield_self { |s| after ? sliced_relation_after(s) : s }
+            .yield_self { |s| before ? sliced_relation_before(s) : s }
+        end
+
+        def after_cursor_date
+          @after_cursor_date ||= after_cursor.first
+        end
+
+        def after_cursor_primary_key
+          @after_cursor_primary_key ||= after_cursor.last
+        end
+
+        def after_cursor
+          @after_cursor ||= super.split(SEPARATOR)
+        end
+
+        def before_cursor_date
+          @before_cursor_date ||= before_cursor.first
+        end
+
+        def before_cursor_primary_key
+          @before_cursor_primary_key ||= before_cursor.last
+        end
+
+        def before_cursor
+          @before_cursor ||= super.split(SEPARATOR)
+        end
+      end
+    end
+  end
+end