Post#fast_count: raise min cache lifetime to 3 minutes (#3925).

app/models/post.rb

@@ -1267,7 +1267,7 @@ class Post < ApplicationRecord
     end
 
     def set_count_in_cache(tags, count, expiry = nil)
-      expiry ||= [count.seconds, 20.hours].min
+      expiry ||= count.seconds.clamp(3.minutes, 20.hours).to_i
 
       Cache.put(count_cache_key(tags), count, expiry)
     end

test/unit/post_test.rb

@@ -2557,7 +2557,7 @@ class PostTest < ActiveSupport::TestCase
         end
 
         should "set the expiration time" do
-          Cache.expects(:put).with(Post.count_cache_key("aaa score:42"), 1, 1)
+          Cache.expects(:put).with(Post.count_cache_key("aaa score:42"), 1, 180)
           Post.fast_count("aaa score:42")
         end
       end