Re: [PATCH] Integer overflow in timestamp[tz]_part() and date/time boundaries check

On 2/24/16, Vitaly Burovoy <vitaly(dot)burovoy(at)gmail(dot)com> wrote:
> On 2/2/16, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
>> On 2/2/16 6:39 PM, Tom Lane wrote:
>>> I'm inclined to think that a good solution would be to create an
>>> artificial restriction to not accept years beyond, say, 100000 AD.
>>> That would leave us with a lot of daylight to not have to worry
>>> about corner-case overflows in timestamp arithmetic. I'm not sure
>>> though where we'd need to enforce such a restriction; certainly in
>>> timestamp[tz]_in, but where else?
>>
>> Probably some of the casts (I'd think at least timestamp->timestamptz).
>> Maybe timestamp[tz]_recv. Most of the time*pl* functions. :/
>
> Please find attached a patch checks boundaries of date/timestamp[tz].
> There are more functions: converting to/from timestamptz, truncating,
> constructing from date and time etc.
>
> I left the upper boundary as described[1] in the documentation
> (294276-12-31 AD), lower - "as is" (4714-11-24 BC).
> It is easy to change the lower boundary to 4713-01-01BC (as described
> in the documentation) and it seems necessary because it allows to
> simplify IS_VALID_JULIAN and IS_VALID_JULIAN4STAMPS and avoid the next
> behavior:
>
> postgres=# select
> postgres-# to_char(date_trunc('week', '4713-01-01 BC'::date),'day')
> postgres-# ,to_char(date_trunc('week', '4714-12-29 BC'::date),'day')
> postgres-# ,to_char(date_trunc('week', '4714-12-28 BC'::date),'day');
> to_char | to_char | to_char
> -----------+-----------+-----------
> monday | monday | thursday
> (1 row)
>
> since 4714-12-28 BC and to the past detection when a week is starting
> is broken (because it is boundary of isoyears -4713 and -4712).
> Is it worth to break undocumented range or leave it as is?
>
> There is one more flaw: checking for a correctness begins from date
> and if default TZ is not UTC, dump/restore of values of type
> timestamptz which are close to allowed boundaries can be broken (and
> such result can't be restored because date is not in allowed range):
> postgres=# SET TIME ZONE 'GMT+1';
> SET
> postgres=# COPY (SELECT '4714-11-24 00:00:00.000000+00
> BC'::timestamptz) TO STDOUT;
> 4714-11-23 23:00:00-01 BC
>
> Also I'm asking for a help because the query (in default TZ='GMT+1'):
> postgres=# SELECT '4714-11-24 00:00:00.000000+00 BC'::timestamptz;
>
> in psql gives a result "4714-11-23 23:00:00-01 BC",
> but in a testing system gives "Sun Nov 23 23:00:00 4714 GMT BC"
> without TZ offset.
>
>
> I don't see what can be added to the documentation with the applied patch.
>
> More testings, finding bugs, uncovered functions, advice, comment
> improvements are very appreciated.
>
> [1]http://www.postgresql.org/docs/devel/static/datatype-datetime.html

I'm sorry, gmail hasn't added a header "In-Reply-To" to the last email.
Previous thread is by the link[2].

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--
Best regards,
Vitaly Burovoy