Thread: BUG #2093: SUM of timeintervals, no problems in 8.0.3

The following bug has been logged online:

Bug reference:      2093
Logged by:          Björn Sjölenius
Email address:      salvium@gmail.com
PostgreSQL version: 8.1
Operating system:   OpenBSD 3.8
Description:        SUM of timeintervals, no problems in 8.0.3
Details:

Just upgraded fron 8.0.5 to 8.1, and a function where I summerize logon time
now give quite odd result. Duplicated the problem;

----------------- Commands to execute ------------------
createdb test
psql test

CREATE TABLE activity_tab (
    nick character varying(32),
    logon timestamp with time zone,
    logoff timestamp with time zone
);

COPY activity_tab (nick, logon, logoff) FROM stdin USING DELIMITERS '|';
apa|2005-11-01 00:00:00+01|2005-11-01 23:00:00+01
apa|2005-11-02 00:00:00+01|2005-11-02 23:00:00+01
apa|2005-11-03 00:00:00+01|2005-11-04 23:00:00+01
\.

SELECT LOWER(nick) AS "nick", SUM(logoff-logon) AS "time"
FROM activity_tab
GROUP BY LOWER(nick);

\q

dropdb test

----------------- End of commands ------------------

The result I get;
 nick |      time
------+----------------
 apa  | 1 day 69:00:00


Expected result is what 8.0.3 give me;
 nick |      time
------+----------------
 apa  | 3 days 21:00:00


Hope you can help! And a BIG THANKYOU for your great work!

Best regards, Björn

Björn Sjölenius wrote:

> The result I get;
>  nick |      time
> ------+----------------
>  apa  | 1 day 69:00:00
>
>
> Expected result is what 8.0.3 give me;
>  nick |      time
> ------+----------------
>  apa  | 3 days 21:00:00

Actually this is expected.  8.1 groups hours and days separately,
because there is no way to know if 1 day means 23, 24 or 25 hours (or
even a fractional number like 24.5) in the presence of a daylight-saving
switch event.  So "1 day 69 hours" is actually more correct.

There is a function to convert to the older format:

alvherre=# select justify_hours('1 day 69:00:00');
  justify_hours
-----------------
 3 days 21:00:00
(1 fila)

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support