Re: [HACKERS] Something for the TODO list: deprecating abstime and friends

On Wed, Jul 19, 2017 at 3:26 PM, Mark Dilger <hornschnorter@gmail.com> wrote:
>> Typically, when you try to store an out-of-range value in PostgreSQL,
>> you get an ERROR, and that's one of the selling points of PostgreSQL.
>> PostgreSQL users regularly beat up other projects for, say, allowing
>> 0000-00-00 to be considered a valid date, or any similar perceived
>> laxity in enforcing data consistency.  I don't like the idea that we
>> can just deviate from that principle whenever adhering to it is too
>> much work.
>
> I don't see the relevance of this statement.  I am not planning to allow
> abstime data that is outside the range of the new epoch.  Attempts to
> cast strings like '1962-07-07 01:02:03' to abstime would draw an
> exception with a suitably informative message.
>
> Now, the objection to having on-disk data automagically change meaning
> is concerning, ...

I see those things as very similar issues, but YMMV.

> ... and I was particularly unsatisfied with the idea that
> NOSTART_ABSTIME and NOEND_ABSTIME would suddenly be
> reinterpreted as seconds in the year 2068, which is why I made mention
> of it upthread.  I was less concerned with dates prior to 1970 being
> reinterpreted, though it is hard to justify why that bothers me less.

I think any change in the meaning of bytes already on disk is a
concern.  It wouldn't bother me to say "these are second-class types,
so if you have columns of this type, pg_upgrade will fail and tell you
that you can't upgrade a database with those columns from a catversion
< X to a catversion > X".  But having it silently work and silently
corrupt your data doesn't seem OK to me.

> Those who feel otherwise might like to also argue for dropping
> float4 because float8 does all the same stuff better.

I don't think that's the same thing, but given my notorious hatred of
floating point arithmetic, it would also bother me less than you might
think.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company