Laurenz Albe <laurenz.albe@cybertec.at> writes:
> On Tue, 2022-07-05 at 19:37 +0900, Tatsuo Ishii wrote:
>> Of course the internal representation of timestamp with time zone data
>> type is not affected by the time zone setting. But why other form of
>> to_timestamp is labeled as stable? If your theory is correct, then
>> other form of to_timestamp shouldn't be labeled immutable as well?
> The result of the two-argument form of "to_timestamp" can depend on
> the setting of "lc_time":
It also depends on the session's timezone setting, in a way that
the single-argument form does not.
regression=# show timezone;
TimeZone
------------------
America/New_York
(1 row)
regression=# select to_timestamp(0);
to_timestamp
------------------------
1969-12-31 19:00:00-05
(1 row)
regression=# select to_timestamp('1970-01-01', 'YYYY-MM-DD');
to_timestamp
------------------------
1970-01-01 00:00:00-05
(1 row)
regression=# set timezone = 'utc';
SET
regression=# select to_timestamp(0);
to_timestamp
------------------------
1970-01-01 00:00:00+00
(1 row)
regression=# select to_timestamp('1970-01-01', 'YYYY-MM-DD');
to_timestamp
------------------------
1970-01-01 00:00:00+00
(1 row)
The two results of to_timestamp(0) represent the same UTC
instant, but the other two are different instants.
regards, tom lane