Re: [HACKERS] Re: [GENERAL] Re: [PHP3] Re: PostgreSQL vs Mysql comparison

> Bruce Momjian <maillist@candle.pha.pa.us> writes:
> > But can we compare aggs and non-aggs?  I see now that our code is fine:
> 
> No, you're barking up the wrong tree.  The issue is whether a HAVING
> clause that doesn't contain *any* aggregates is legal/reasonable.
> It can contain non-aggregated references to GROUP BY columns in
> any case.  But without aggregates, there's no semantic difference
> from putting the same condition in WHERE.
> 
> I believe that planner.c currently has an implementation assumption
> that HAVING must have an aggregate (because it hangs the HAVING clause
> onto the Agg plan node as a qual clause --- if no Agg node, no place to
> perform the HAVING test).  This could be fixed if we felt it was worth
> doing.
> 
> I can't get excited about changing this from the standpoint of
> functionality, because AFAICS there is no added functionality.
> But if we're looking bad on a recognized benchmark maybe we
> should do something about it.

Agreed.  I think there are too many people who get HAVING confused to
allow it.  Better that we should prevent it and make them do it right.

--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
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