serial type (text instead of integer) and duplicate keys

Hello all!

There is an extrange error in my logfile:

update articles set online='t' where id = 391 ;
ERROR: duplicate key violates unique constraint "articles_pkey"

(the error exists only with this id)

I've checked (well, almost imposible) if there was more than one
article with this id:

select count(*) from articles where id=391 ;
count
-------
1
(1 row)

Then, I checked the table:

Table "public.articles"
Column | Type | Modifiers
-------------------+------------------------+-----------------------------------------------------
id | integer | not null default
nextval('"articles_id_seq"'::text)

Here is the origin of my problem, I think: "text". "text"?. The
"serial" type generate text instead of integer. Really extrange.

So, my next query:
select id from articles where id like '%391%' ;
id
-----
391
391
(2 rows)

The problem is easy to solve: delete and re-create the rows. But I
would like to know the origin of this error. Any tip?

Thanks in advance,
Carlos

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