Re: A query that doesn't work on 7.1

Tom Lane wrote:

> > Here's another twist though. Is this a bug too or is this just beyond our reach?
>
> > psql:lead1.sql:64: ERROR: Unable to select an aggregate function avg(date)
>
> It's just that we don't have any avg() function for date --- nor for
> timestamp, which is a little more surprising.
>

FYI:
I got by with kind of a pseudo average (mean, I guess) for now implemented as:

min(date) + (max(date) - min(date)/2)

>
> You could probably gin up a usable avg(timestamp) using the avg(float8)
> routines, since a timestamp is really just a double under the hood.
>

When you say "gin up" are you talking about C, PL/XXX, or just casts?

BTW, here's another question:

Here's a view of a union. The two selects are fast when executed individually (and
explain confirms that they use indexes). When I query the view, though, it is slow
(explain says the scans are sequential).

Is this expected or a bug?

-- Simulate a table of lead times
create view vend_v_lead as select
p.pnum as pnum,'vend' as type,ldtime::float8 as lead,0 as aging from vend_price v,
prd_part p where v.pnum = p.pnum
union select

p.pnum,'hist',date_part('day',(m.tdate::datetime-m.mtr_date::datetime)::timespan),0
from mtr_reg m, prd_part p where m.pnum = p.pnum and m.ttype = 'po' and m.status =
'clsd'
;