On 06/15/2018 12:24 PM, Jeremy Finzel wrote:
Hello!
We often prefer to use timestamptz or "timestamp with time zone" in our
environment because of its actually storing "objective time" with
respect to UTC. But in my own work experience, I have scarcely
encountered a case where business users, and software engineers, do not
actually think it means the opposite.
When I say "timestamp with time zone", people think the data is saved
*in* a specific time zone, whereas in reality, the opposite is true. It
is really more like "timestamp UTC" or you even could say "timestamp at
UTC". When you query this of course, then it shows you the time offset
based on your client timezone setting.
I do believe this is part of the SQL standard, but I have found that it
creates great confusion. I think many devs choose timestamp instead of
timestamptz because they don't really understand that timestamptz gives
you UTC time storage built-in.
That of course means that if you have multiple servers that run in a
different time zone, and you want to replicate that data to a
centralized location, you can easily figure out what objective time a
record changed, for instance, not knowing anything about what time zone
the source system is in.
So it seems to me that "timestamp with time zone" is a misnomer in a big
It actually is. It is just one timezone though, UTC.
way, and perhaps it's worth at least clarifying the docs about this, or
https://www.postgresql.org/docs/10/static/datatype-datetime.html#DATATYPE-TIMEZONES
"For timestamp with time zone, the internally stored value is always in
UTC (Universal Coordinated Time, traditionally known as Greenwich Mean
Time, GMT). An input value that has an explicit time zone specified is
converted to UTC using the appropriate offset for that time zone. If no
time zone is stated in the input string, then it is assumed to be in the
time zone indicated by the system's TimeZone parameter, and is converted
to UTC using the offset for the timezone zone."
How should the above be clarified?
even renaming the type or providing an aliased type that means the same
thing, something like timestamputc. Maybe I'm crazy but I would
appreciate any feedback on this and how easily it confuses.
Thanks,
Jeremy
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
