Anand Raman <araman(at)india-today(dot)com> writes:
> arttoday=# \copy artists from STDIN using delimiters '|' with null as '||';
Er, don't you mean "with null as ''"?
The above-given command will never think any input column is a null,
since it won't parse '||' as a column value in the first place.
regards, tom lane