Update of two tables in a trigger

Hello world,

I am currently playing with postgres to learn a bit about it. I
created a database to contain information about manpages i printed.
(I am going to print a lot of them, and I don't want to do it
twice).

For some reason, I split the output in two tables, one to contain
the command and the section number, one for the number of pages and
sheets of paper, and the date I printed it.

I connected these two tables by creating a sequence, using the
nextval() as default value for a field in the first table and the
currval() as default in the second.

I also created a view (named v_manpages) that joins these two tables
together, based on the mentioned fields.

After failing to get it to work with rules, I am now trying to use
triggers and PL/pgSQL-functions for updating the view, but I am
experiencing rather strange things. The inserting of rows works
fine, but deleting...

Here's my problem:

manpage=> select * from v_manpages;
cmd |section|pages|sheets| when
----------+-------+-----+------+----------
procmailsc|5 | 5| 3|1999-05-24
sox |1 | 11| 6|1999-05-24
chgrp |1 | 1| 1|1999-05-24
procmailrc|5 | 14| 7|1999-05-24

manpage=> insert into v_manpages values ('update','sql',1,1);
INSERT 20036 1
manpage=> insert into v_manpages values ('test'1,2,1);
INSERT 20039 1

manpage=> select * from v_Manpages;
cmd |section|pages|sheets| when
----------+-------+-----+------+----------
procmailsc|5 | 5| 3|1999-05-24
sox |1 | 11| 6|1999-05-24
chgrp |1 | 1| 1|1999-05-24
procmailrc|5 | 14| 7|1999-05-24
update |sql | 1| 1|1999-05-24
test |1 | 2| 1|1999-05-24

manpage=> delete from v_manpages where cmd = 'sox';
DELETE 1
manpage=> select * from v_Manpages;
cmd |section|pages|sheets| when
----------+-------+-----+------+----------
procmailsc|5 | 5| 3|1999-05-24
sox |1 | 11| 6|1999-05-24
chgrp |1 | 1| 1|1999-05-24
procmailrc|5 | 14| 7|1999-05-24

Two are gone, sox is still present.

manpage=> delete from v_manpages where cmd = 'sox';
DELETE 0

Now I can't delete anything more.

These are my tables, triggers and functions:

--------------

create table manpages (cmd text, section varchar(5), prnr int4
unique default nextval('seq_printnr'));

create table info (prnr int4 unique default currval('seq_printnr'),
pages int2, sheets int2, when date default current_date);

create view v_manpages as select cmd,section,pages,sheets,when from
manpages,info where manpages.prnr = info.prnr);

create function get_prnrfromcmd(text) returns int4 as '
select prnr from manpages where cmd = $1;
' language 'sql';

create function tp_v_manpages () returns opaque as '
declare
printnr int4;
begin
if TG_OP = ''DELETE'' then
printnr = get_prnrfromcmd(OLD.cmd);
if printnr ISNULL then
return NULL;
end if;

delete from manpages where prnr = printnr;
delete from info where prnr = printnr;
return OLD;
end if;

if TG_OP = ''INSERT'' then
insert into manpages values (NEW.cmd,
NEW.section);

printnr := get_prnrfromcmd(NEW.cmd);
if printnr ISNULL then
return NULL;
end if;

insert into info values (printnr, NEW.pages,
NEW.sheets);
return NEW;
end if;
return NULL;
end;
' language 'plpgsql';

create trigger t_v_manpages
before insert or delete on v_manpages for each row
execute procedure tp_v_manpages();

------------

PostgreSQL version is 6.4.2.

What mistake did I make?

(If this mail is too long, or if there is information missing,
or if I am a complete fool, I'm very sorry. But please help me.)

--
Christian Ullrich

(I am a student, I live in Germany)