timestamp and date behaviour with '-infinity'

Started by Russell Smithover 21 years ago3 messagesgeneral
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#1Russell Smith
mr-russ@pws.com.au

Timestamps support infinity. However if appears dates do not.

When timestamps are cast to dates, there is no output. Is this an acceptable option or not?

Below are a number of examples showing what I am experiencing.

The last own shows how converting timestamps to dates and then ordering doesn't give you the
order you want. Maybe you should just order by the timestamp to begin with. However
Date does not understand infinity at all.

So as much as what I have said is confusing.

1. Is the output acceptable?
2. should there be infinity support for dates?
3. if not, how should -infinity timestamp converted to a date.
4. Am I missing the point here.

Regards

Russell Smith

church=# select '-infinity'::timestamp;
timestamp
-----------
-infinity
(1 row)

church=# select '-infinity'::timestamp::date;
date
------

(1 row)

church=# select '*' || '-infinity'::timestamp::date || '*';
?column?
----------

(1 row)

church=# select '*' || '-infinity'::timestamp::date::text || '*';
?column?
----------

(1 row)

church=# select '*' || '-infinity'::timestamp || '*';
?column?
-------------
*-infinity*
(1 row)

church=# select '*' || '-infinity'::timestamp::date || '*';
?column?
----------

(1 row)

church=# select '-infinity'::timestamp::date as a, '-inf' UNION select 'infinity'::timestamp::date as a, 'inf' ORDER BY a ASC;
a | ?column?
---+----------
| -inf
| inf
(2 rows)

church=# select '-infinity'::timestamp::date as a, '-inf' UNION select 'infinity'::timestamp::date as a, 'inf' ORDER BY a DESC;
a | ?column?
---+----------
| -inf
| inf
(2 rows)

church=# select '-infinity'::timestamp::date::timestamp;
timestamp
-----------

(1 row)

#2Stephan Szabo
sszabo@megazone23.bigpanda.com
In reply to: Russell Smith (#1)
Re: timestamp and date behaviour with '-infinity'

On Mon, 30 Aug 2004, Russell Smith wrote:

Timestamps support infinity. However if appears dates do not.

When timestamps are cast to dates, there is no output. Is this an acceptable option or not?

It looks to me that it turns into a NULL date. I'm not sure why it's
doing that rather than an error, though.

#3Tom Lane
tgl@sss.pgh.pa.us
In reply to: Russell Smith (#1)
Re: timestamp and date behaviour with '-infinity'

Russell Smith <mr-russ@pws.com.au> writes:

Timestamps support infinity. However if appears dates do not.

There is a TODO item to fix that, but it hasn't gotten to the top of
anyone's priority list ...

regards, tom lane