Re: [PATCH] Erase the distinctClause if the result is unique by definition

On Thu, Feb 13, 2020 at 5:39 PM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:

> On Tue, Feb 11, 2020 at 10:06:17PM +0530, Ashutosh Bapat wrote:
> > On Tue, Feb 11, 2020 at 8:27 AM Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com>
> wrote:
> >
> > > On Tue, Feb 11, 2020 at 12:22 AM Ashutosh Bapat <
> > > ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
> > >
> > >>>
> > >>> [PATCH] Erase the distinctClause if the result is unique by
> > >>> definition
> > >>
> > >> I forgot to mention this in the last round of comments. Your patch was
> > >> actually removing distictClause from the Query structure. Please avoid
> > >> doing that. If you remove it, you are also removing the evidence that
> this
> > >> Query had a DISTINCT clause in it.
> > >
> > > Yes, I removed it because it is the easiest way to do it. what is the
> > > purpose of keeping the evidence?
> > >
> >
> > Julien's example provides an explanation for this. The Query structure is
> > serialised into a view definition. Removing distinctClause from there
> means
> > that the view will never try to produce unique results.
>
> And also I think that this approach will have a lot of other unexpected
> side
> effects. Isn't changing the Query going to affect pg_stat_statements
> queryid
> computing for instance?
>

Thanks, the 2 factors above are pretty valuable. so erasing the
distinctClause is not reasonable, I will try another way.