Re: group by not returning sorted rows

On Mon, 5 Apr 2004, Bret Hughes wrote:

> select cities.name as city, buildings.name as building,
>     pagename,
>     log_date ,
>     sum(exhibition_count) as tot
> from logrecords
>     join cities on (logrecords.city=cities.num)
>     join buildings on (logrecords.building=buildings.num)
> where     advertiser = 'Nielsens' and
>     log_date >= '01/01/2004' and
>     log_date <= '01/31/2004'
> group by cities.name, buildings.name,pagename,log_date ;
>
> I have migrated a database from a redhat 7.3 box running
> [bhughes@compaq3 reports]$ rpm -q postgresql
> postgresql-7.2.3-5.73
>
> To a redhat 9 box running :
> [bhughes@compaq2 reports]$ rpm -q postgresql
> postgresql-7.4.2-1PGDG
>
> and the rows resulting from the query are no longer sorted by log date.
> Is this a change since 7.2x?

Yes.

> I can achieve the results I need by adding an order by clause identical
> to the group by but this seems counter intuitive since the rows have to
> be ordered anyway.

They no longer need to always be pre-ordered in order to do the group by
(this depends on plan).