BUG #1188: evaluation order of select seems to be wrong

The following bug has been logged online:

Bug reference: 1188
Logged by: Holger Jakobs

Email address: holger(at)jakobs(dot)com

PostgreSQL version: 7.4

Operating system: Linux

Description: evaluation order of select seems to be wrong

Details:

There is a table like

create table games (
teamnr serial,
player integer not null,
win integer not null,
lose integer not null
);

I have the following select statement:

select teamnr, sum(win)/sum(lose)
from games
group by teamnr
having sum(lose) > 0;

According to what I know about select, the expressions of the from clause
have to be evaluated last, so that the case that sum(lose) is zero will be
filtered _before_ the division by 0 takes place.

Unfortunately, PostgreSQL 7.4.2 gives a "division by zero" error if there
are teams which have not yet won any game. Those teams should just not
appear in the output.

Example insert statements:

insert into games values (1, 11, 3, 0);
insert into games values (1, 12, 5, 2);
insert into games values (2, 21, 6, 0);

Without the last insert everything works fine. Adding the last insert
produces a team with zero numbers of games won leading to the error.

Btw, Oracle 8 handels this correctly.