Re: Replication vs. float timestamps is a disaster

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Replication vs. float timestamps is a disaster
Date: 2017-02-20 14:07:33
Message-ID: 31590.1487599653@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-02-20 11:58:12 +0100, Petr Jelinek wrote:
>> That being said, I did wonder myself if we should just deprecate float
>> timestamps as well.

> I think we need a proper deprecation period for that, given that the
> conversion away will be painful for pg_upgrade using people with big
> clusters. So I think we should fix this regardless... :(

The question to be asked is whether there is still anybody out there
using float timestamps. I'm starting to get dubious about it myself.
Certainly, no packager that I'm aware of has shipped a float-timestamp
build since we switched the default in 8.4. Maybe there is somebody
who's faithfully built a float-timestamp custom build every year so they
can pg_upgrade in place from their 8.3 installation, but there have got
to be darn few such people.

As for "proper deprecation period", the documentation has called the
option deprecated since 8.4:

-disable-integer-datetimes
Disable support for 64-bit integer storage for timestamps and
intervals, and store datetime values as floating-point numbers
instead. Floating-point datetime storage was the default in
PostgreSQL releases prior to 8.4, but it is now deprecated,
because it does not support microsecond precision for the full
range of timestamp values.

I think the strongest reason why we didn't move to kill it sooner was
that we were not then assuming that every platform had 64-bit ints;
but we've required that since 9.0.

regards, tom lane

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