title: mysql adding /dropping indexes and foreign key in one statement
body: <p>I have the following code:</p>
  
  <pre><code>alter table a 
  add index a_idx1(a1,b1,c1),
  add index a_idx2(d1),
  add index b_idx(d3),
  add constraint fk_1 foreign key(f1) references b(f2) on update restrict on delete restrict,
  drop primary key,
  add primary key(e2)
  </code></pre>
  
  <p>I initially had done it in separate steps, but to avoid locking issues etc, I did it in one, but it tends to sometimes degrade performance and weirdly sometimes bring down the database. </p>
  
  <p>Is there anything in this statement that might do something to the db?</p>