Revert "Improves the performance of the Redis set cache"

This reverts commit 389e6f58.

lib/gitlab/repository_cache_adapter.rb

@@ -58,16 +58,11 @@ module Gitlab
         # wrong answer. We handle that by querying the full list - which fills
         # the cache - and using it directly to answer the question.
         define_method("#{name}_include?") do |value|
-          return __send__(name).include?(value) if strong_memoized?(name) # rubocop:disable GitlabSecurity/PublicSend
-
-          # If the member exists in the set, return as such early.
-          return true if redis_set_cache.include?(name, value)
-
-          # If it did not, make sure the collection exists.
-          # If the collection exists, then item does not.
-          return false if redis_set_cache.exist?(name)
+          if strong_memoized?(name) || !redis_set_cache.exist?(name)
+            return __send__(name).include?(value) # rubocop:disable GitlabSecurity/PublicSend
+          end
 
-          __send__(name).include?(value) # rubocop:disable GitlabSecurity/PublicSend
+          redis_set_cache.include?(name, value)
         end
       end
 

lib/gitlab/repository_set_cache.rb

@@ -25,7 +25,7 @@ module Gitlab
     end
 
     def read(key)
-      with { |redis| redis.sscan_each(cache_key(key)).to_a }
+      with { |redis| redis.smembers(cache_key(key)) }
     end
 
     def write(key, value)
@@ -47,10 +47,11 @@ module Gitlab
     end
 
     def fetch(key, &block)
-      result = read(key)
-      return result unless result.empty?
-
-      write(key, yield)
+      if exist?(key)
+        read(key)
+      else
+        write(key, yield)
+      end
     end
 
     def include?(key, value)