Re: LEFT JOINs not optimized away when not needed

On Wed, Jul 9, 2014 at 1:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Right.  Yeah, I was not that excited about its usefulness either.
> However, the OP seems to think that it's a common optimization
> (I wonder if he can cite chapter and verse on which other DBMSes
> do it).
>

I make no claim about its commonness, but I think this type of optimization
is very useful when selecting a limited subset of the columns from a
complex view, particularly where the output rows are expected to be
distinct on the exact set of columns that are selected.


Moshe Jacobson
Manager of Systems Engineering, Nead Werx Inc. <http://www.neadwerx.com>
2323 Cumberland Parkway =C2=B7 Suite 201 =C2=B7 Atlanta, GA 30339

"Quality is not an act, it is a habit." -- Aristotle