Re: BUG #17687: Session timezone change does not play well with prepared statements

PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> When a statement is prepared using one session timezone and executed using
> another, it returns the wrong timestamp.

> Example using psql:
> postgres=# SET TIMEZONE TO 'Europe/Berlin';
> SET
> postgres=# PREPARE test AS
> SELECT '2021-03-15 14:10:03'::timestamptz;
> PREPARE
> postgres=# SET TIMEZONE TO 'America/Chicago';
> SET
> postgres=# EXECUTE test;
> timestamptz
> ------------------------
> 2021-03-15 08:10:03-05
> (1 row)

That is not a bug, it's just how timestamptz works. You'd get the
same behavior if you stored the value into a table and then read
it out under another timezone setting. (Internally, the reason
is that the timestamptz literal is reduced to a Const on sight,
and stored that way in the prepared statement.)

regards, tom lane