mysql query building output taking a long time

I have a simple query that does

 select * 
   from t 
  limit 1; 

on a remote mysql server.

I use squirrel(mysql client) to run it, 开发者_运维问答it shows:

Query 1 of 1 elapsed time (seconds) - Total: 22.047, SQL query: 1.047, Building output: 21

why does building output take such a long time? what does this process do? when running from mysql command line, the whole process takes 0.3 secs (also remotely)