Forum: Ruby on Rails strange query like SELECT * FROM [Primary Key] = 0

I am use ROR v= 2.3.4

in my console.  i found a strange query SELECT * FROM [Primary Key(id)] 
=
0,
because of i had changed the id[Primary Key] from int to varchar. ruby 
on
rails still query the db on int like 0 use int not '0'.
such kind query cost too much db resource. and i don't konw how to 
prevent
such query.

please help.