Speedup iterating over WorkSet (#5559)

lib/sidekiq/api.rb

@@ -1103,15 +1103,23 @@ module Sidekiq
 
     def each(&block)
       results = []
+      procs = nil
+      all_works = nil
+
       Sidekiq.redis do |conn|
-        procs = conn.sscan_each("processes").to_a
-        procs.sort.each do |key|
-          valid, workers = conn.pipelined { |pipeline|
-            pipeline.exists?(key)
+        procs = conn.sscan_each("processes").to_a.sort
+
+        all_works = conn.pipelined do |pipeline|
+          procs.each do |key|
             pipeline.hgetall("#{key}:work")
-          }
-          next unless valid
+          end
+        end
+      end
+
+      procs.zip(all_works).each do |key, workers|
         workers.each_pair do |tid, json|
+          next if json.empty?
+
           hsh = Sidekiq.load_json(json)
           p = hsh["payload"]
           # avoid breaking API, this is a side effect of the JSON optimization in #4316
@@ -1119,7 +1127,6 @@ module Sidekiq
           results << [key, tid, hsh]
         end
       end
-      end
 
       results.sort_by { |(_, _, hsh)| hsh["run_at"] }.each(&block)
     end