Re: Why *exactly* is date_trunc() not immutable ?

On Feb 18, 2007, at 20:29 , Karsten Hilbert wrote:

> What I don't understand, however, is exactly *why* date_trunc is
> not immutable ?

I believe it's because the result of date_trunc depends on the time
zone setting for the session.

test=# select date_trunc('day', current_timestamp);
        date_trunc
------------------------
2007-02-18 00:00:00+09
(1 row)

test=# set time zone 'EST5EDT';
SET
test=# select date_trunc('day', current_timestamp);
        date_trunc
------------------------
2007-02-18 00:00:00-05
(1 row)

So, given the same arguments, ('day', and current_timestamp),
date_trunc is returning two different results. (Casting to date has
the same issue.)

Michael Glaesemann
grzm seespotcode net