<radha(dot)manohar(at)ndsu(dot)nodak(dot)edu> writes:
> I would like to know how postgresql differentiates between the SQL
> commands that are
> entered by the user and the SQL commands that are executed internally by
> the system
> (for eg, to check the permissions of the user etc)?
There are no such "internal SQL commands". Permissions checking is
hard-coded in C in the backend.
regards, tom lane