Memoize the Paginator#page method

This method is invoked multiple times to retrieve the `start_cursor`,
the `end_cursor`, and ultimately to return the actual `page` record.
By memoizing it, we avoid it from mapping over the `records` again and
again and rebuilding all the cursors every time it is invoked.

CHANGELOG.md

@@ -20,6 +20,7 @@ These are the latest changes on the project's `master` branch that have not yet
 
 ### Fixed
 - Only trigger one SQL query to load the records from the database and use it to determine if there was a previous / is a next page
+- Memoize the `Paginator#page` method which is invoked multiple times to prevent it from mapping over the `records` again and again and rebuilding all cursors
 
 ### Added
 - Description about `order_by` on arbitrary SQL to README.md

lib/rails_cursor_pagination/paginator.rb

@@ -147,11 +147,13 @@ def page_info
     #
     # @return [Array<Hash>] List of hashes, each with a `cursor` and `data`
     def page
-      records.map do |item|
-        {
-          cursor: cursor_for_record(item),
-          data: item
-        }
+      memoize :page do
+        records.map do |item|
+          {
+            cursor: cursor_for_record(item),
+            data: item
+          }
+        end
       end
     end