teledb=# create table t_upper(id int,mc text);
CREATE TABLE
teledb=# create index t_upper_mc on t_upper(mc);  
CREATE INDEX
teledb=# insert into t_upper select t,md5(t::text) from generate_series(1,10000) as t;
INSERT 0 10000
teledb=# analyze t_upper;
ANALYZE
teledb=# explain select * from t_upper where upper(mc)=md5('1');
                               QUERY PLAN                           
------------------------------------------------------------------------
 Remote Fast Query Execution  (cost=0.00..0.00 rows=0 width=0)
   Node/s: dn01, dn02
   ->  Seq Scan on t_upper  (cost=0.00..133.58 rows=25 width=37)
         Filter: (upper(mc) = 'c4ca4238a0b923820dcc509a6f75849b'::text)
(4 rows)

teledb=# create index t_upper_mc on t_upper(upper(mc)); 
ERROR:  relation "t_upper_mc" already exists

teledb=# create index t_upper_mc1 on t_upper(upper(mc)); 
CREATE INDEX
teledb=# explain select * from t_upper where upper(mc)=md5('1');
                                    QUERY PLAN                                
----------------------------------------------------------------------------------
 Remote Fast Query Execution  (cost=0.00..0.00 rows=0 width=0)
   Node/s: dn01, dn02
   ->  Bitmap Heap Scan on t_upper  (cost=4.48..50.94 rows=25 width=37)
         Recheck Cond: (upper(mc) = 'c4ca4238a0b923820dcc509a6f75849b'::text)
         ->  Bitmap Index Scan on t_upper_mc1  (cost=0.00..4.47 rows=25 width=0)
               Index Cond: (upper(mc) = 'c4ca4238a0b923820dcc509a6f75849b'::text)
(6 rows)