From: Tom Lane <tgl@sss.pgh.pa.us>
To: email@piotr-stefaniak.me
Cc: pgsql-bugs@postgresql.org
Subject: Re: BUG #14479: Casting non-constant values to INTERVAL DAY TO MINUTE doesn't truncate the seconds field
Date: Tue, 27 Dec 2016 13:12:48 -0500
Message-ID: <26632.1482862368@sss.pgh.pa.us> (raw)
In-Reply-To: <20161227172307.10135.7747@wrigleys.postgresql.org>
References: <20161227172307.10135.7747@wrigleys.postgresql.org>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-bugs>
email@piotr-stefaniak.me writes:
> # SELECT x.y::INTERVAL DAY TO MINUTE, (interval '02:47:15.375721')::INTERVAL
> DAY TO MINUTE FROM (VALUES (interval '02:47:15.375721')) x (y);
> y | interval
> -----------------+----------
> 02:47:15.375721 | 02:47:00
> I chose 9.4.10 as the version in the web form because that's what I have,
> but Andrew Gierth has said that this is the behavior of versions: 9.2, 9.3,
> and 9.4 but not versions 9.1, 9.5, and HEAD.
Thanks for the report. It appears that interval_transform is broken:
it's deciding that the cast to INTERVAL DAY TO MINUTE is a no-op and
can be replaced by a RelabelType.
This has *not* been fixed in HEAD, it's just been masked in this
particular example by other changes. You can show it's still broken with
regression=# create table tt (f1 interval);
CREATE TABLE
regression=# insert into tt values('02:47:15.375721');
INSERT 0 1
regression=# select f1 from tt;
f1
-----------------
02:47:15.375721
(1 row)
regression=# select f1::INTERVAL DAY TO MINUTE from tt;
f1
-----------------
02:47:15.375721
(1 row)
This case fails all the way back to 9.2 where transforms were introduced.
The reason your example happens not to fail in 9.5 and up is that those
versions know how to flatten a single-row VALUES construct, so that the
cast gets simplified to a constant (correctly) and interval_transform
is never applied.
I've not figured out exactly what's broken about interval_transform;
the bit-twiddling looks a bit fishy, but it may be that that's fine
and there's simply a thinko in the logic about which conversions
are no-ops.
regards, tom lane
--
Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-bugs
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, email@piotr-stefaniak.me
Subject: Re: BUG #14479: Casting non-constant values to INTERVAL DAY TO MINUTE doesn't truncate the seconds field
In-Reply-To: <26632.1482862368@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox