Re: [HACKERS] Re: [BUGS][PATCH] BUG #14486: Inserting and selectinginterval have different constraints - Mailing list pgsql-hackers

On 1/5/17, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Vitaly Burovoy <vitaly.burovoy@gmail.com> writes:
>> On 1/5/17, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> We could think about replacing interval2tm's output format with some
>>> other struct that uses a TimeOffset for hours and so cannot overflow.
>>> I'm not sure though how far the effects would propagate; it might be
>>> more work than we want to put into this.
>
>> If values with overflow are already in a database, what do you expect
>> a new output function should fix?
>
> My point is that ideally, any value that can physically fit into struct
> Interval ought to be considered valid.  The fact that interval_out can't
> cope is a bug in interval_out, which ideally we would fix without
> artificially restricting the range of the datatype.
>
> Now, the problem with that of course is that it's not only interval_out
> but multiple other places.  But your proposed patch also requires touching
> nearly everything interval-related, so I'm not sure it has any advantage
> that way over the less restrictive answer.

OK, I try to limit values from
9223372036854775807/3600000000/24/365=292471.2 years
to
7730941132800000000/3600000000/24/365=245146.5 years

i.e. cut 47325 years or ~16%, but it is only for interval's part
measured in seconds.

Am I correct that we are still limited by ECPG which is limited by the
system "tm" struct?
Also users who use a binary protocol can also use the "tm" struct and
can not expect overflow.

The docs say[1] the highest value of the interval type is 178_000_000
years which is
significantly bigger than both of values (current and limited)
measured in seconds.
I don't think applying that limitation is a big deal.


I tried to find functions should be touched and there are not so many of them:

-- internal functions:
interval_check_overflow(Interval *i)
tm2interval(struct pg_tm * tm, fsec_t fsec, Interval *span)
interval2tm(Interval span, struct pg_tm * tm, fsec_t *fsec)
intervaltypmodleastfield(int32 typmod)

-- output functions:
interval_out(PG_FUNCTION_ARGS)  -- skip output
interval_send(PG_FUNCTION_ARGS) -- skip output

-- main input/computing functions:
interval_in(PG_FUNCTION_ARGS)   -- forgot to cover
interval_recv(PG_FUNCTION_ARGS) -- covered
make_interval(PG_FUNCTION_ARGS) -- covered

AdjustIntervalForTypmod(Interval *interval, int32 typmod)  -- can lead
to overflow

interval_justify_interval(PG_FUNCTION_ARGS)  -- can lead to overflow
interval_justify_hours(PG_FUNCTION_ARGS)  -- can lead to overflow
interval_justify_days(PG_FUNCTION_ARGS)  -- can lead to overflow
interval_um(PG_FUNCTION_ARGS)  -- covered
interval_pl(PG_FUNCTION_ARGS)  -- covered
interval_mi(PG_FUNCTION_ARGS)  -- covered
interval_mul(PG_FUNCTION_ARGS) -- covered

-- can not lead to overflow
interval_transform(PG_FUNCTION_ARGS)
interval_div(PG_FUNCTION_ARGS)
interval_trunc(PG_FUNCTION_ARGS)
interval_part(PG_FUNCTION_ARGS)

-- based on other functions
interval_scale(PG_FUNCTION_ARGS)     -- based on AdjustIntervalForTypmod
interval_accum(PG_FUNCTION_ARGS)     -- based on interval_pl
interval_accum_inv(PG_FUNCTION_ARGS) -- based on interval_mi
interval_avg(PG_FUNCTION_ARGS)       -- based on interval_pl
interval_combine(PG_FUNCTION_ARGS)   -- based on interval_pl
mul_d_interval(PG_FUNCTION_ARGS)     -- based on interval_mul

-- checking, not changing:
interval_finite(PG_FUNCTION_ARGS)
interval_smaller(PG_FUNCTION_ARGS)
interval_larger(PG_FUNCTION_ARGS)
interval_cmp_value(const Interval *interval)
interval_cmp_internal(Interval *interval1, Interval *interval2)
interval_eq(PG_FUNCTION_ARGS)
interval_ne(PG_FUNCTION_ARGS)
interval_lt(PG_FUNCTION_ARGS)
interval_gt(PG_FUNCTION_ARGS)
interval_le(PG_FUNCTION_ARGS)
interval_ge(PG_FUNCTION_ARGS)
interval_cmp(PG_FUNCTION_ARGS)
interval_hash(PG_FUNCTION_ARGS)

-- not applicable:
intervaltypmodin(PG_FUNCTION_ARGS)
intervaltypmodout(PG_FUNCTION_ARGS)
timestamp_pl_interval(PG_FUNCTION_ARGS)
timestamp_mi_interval(PG_FUNCTION_ARGS)
timestamptz_pl_interval(PG_FUNCTION_ARGS)
timestamptz_mi_interval(PG_FUNCTION_ARGS)


=====
In fact, only six of them (not "touching nearly everything
interval-related") should be covered:

* interval_in
* interval_out (yes, the SAMESIGN there is useless)
* AdjustIntervalForTypmod
* interval_justify_interval
* interval_justify_hours
* interval_justify_days


[1]https://www.postgresql.org/docs/current/static/datatype-datetime.html
-- 
Best regards,
Vitaly Burovoy