pg_restore and users

Dear all,
I normally don't do a lot of pg_dump and pg_restore.  And it is not easy 
to experiment with this.
Just trying to clarify something.

While I was using a user name that have rights to createdb, createuser 
to restore the database

pg_restore -d mydb mydb.tar

the program exited with error message: user abs does not exist.

then I created that user with the command createuser abc.
the restore can be finished (actually I have a few users, I have to do 
all of them).

1.  Do I have such problem if I use the super user  POSTGRES?
2. Is the database intended to store a lot of users or only a few?  If 
you have a lot users and you forgot about them, it could be very 
difficult to restore the database.

Anyone can tell me about the normal way of dealing with this.  Or I am 
doing something wrong.


Kemin



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