CHECK constraint fails when it's not supposed to - Mailing list pgsql-general

Hi All,

I encountered an odd issue regarding check constraints complaining
when they're not really violated.

For this particular machine, I am running 8.3.7, but on a machine
running 8.3.5, it seems to have succeeded.  I also upgraded a third
machine from 8.3.5 to 8.3.7, and the query succeeded (so I'm
thinking
it's not related to different postgres versions)

I have a table called "m_class" and the definition is something like
this:

> tii=# \d m_class
>                                               Table "public.m_class"
>          Column          |           Type
> |                          Modifiers
> -------------------------+--------------------------
> +--------------------------------------------------------------
>  id                      | integer                  | not null
> default nextval(('m_class_id_seq'::text)::regclass)
>  class_type              | smallint                 | not null
>  title                   | character varying(100)   | not null
> ...snip...
> date_setup              | timestamp with time zone | not null
> default ('now'::text)::date
>  date_start              | timestamp with time zone | not null
>  date_end                | timestamp with time zone | not null
>  term_length             | interval                 | not null
> default '5 years'::interval
> ...snip...
>  max_portfolio_file_size | integer                  |
> Indexes:
>     "m_class_pkey" PRIMARY KEY, btree (id)
>     "m_class_account_idx" btree (account)
>     "m_class_instructor_idx" btree (instructor)
> Check constraints:
>     "end_after_start_check" CHECK (date_end >= date_start)
>     "end_within_term_length" CHECK (date_end <= (date_start +
> term_length))
>     "min_password_length_check" CHECK
> (length(enrollment_password::text) >= 4)
>     "positive_term_length" CHECK (term_length > '00:00:00'::interval)
>     "start_after_setup_check" CHECK (date_start >= date_setup)
> ...snip...

When I run my update, it fails:
> tii=# begin; update only "public"."m_class" set date_end='2009-09-03
> 05:38:24.030331-07',term_length='177 days 17:59:09.868431' where
> id='2652020';
> BEGIN
> ERROR:  new row for relation "m_class" violates check constraint
> "end_within_term_length"
> tii=# rollback;
> ROLLBACK

The data reads:
> tii=# select date_start, date_end, term_length, '2009-09-03
> 05:38:24.030331-07'::timestamptz - date_start AS new_term_length
> from m_class where id = 2652020;
>          date_start          |          date_end           |
> term_length |     new_term_length
> -----------------------------+-----------------------------
> +-------------+--------------------------
>  2009-03-09 11:39:14.1619-07 | 2009-04-08 11:39:14.1619-07 | 30
> days     | 177 days 17:59:09.868431


Based on new_term_length, the update should succeed.  However, it
doesn't.  Would anyone have an explanation?

Thanks for your help!
--Richard