Re: Optimizing maximum/minimum queries (yet again) - Mailing list pgsql-hackers

Tom Lane wrote:
> Specifically, I'm imagining that we could convert
> 
>     SELECT min(x), max(y) FROM tab WHERE ...
> 
> into sub-selects in a one-row outer query:
> 
>     SELECT (SELECT x FROM tab WHERE ... ORDER BY x LIMIT 1),
>            (SELECT y FROM tab WHERE ... ORDER BY y DESC LIMIT 1);

Does this transformation work for a query of the form:
    SELECT min(x), max(y) FROM tab WHERE random() > 0.5;

(which isn't a very useful query, but I'm sure you can imagine a more 
realistic example involving volatile functions in the WHERE clause.)

-Neil