Use multiple conflict_target in ON CONFLICT clause

Question

I have two columns in table col1, col2, they both are unique indexed (col1 is unique and so is col2).

I need at insert into this table, u

Answer 1

ON CONFLICT is very clumsy solution, run

UPDATE dupes SET key1=$1, key2=$2 where key3=$3    
if rowcount > 0    
  INSERT dupes (key1, key2, key3) values ($1,$2,$3);

works on Oracle, Postgres and all other database