Re: Use extended statistics to estimate (Var op Var) clauses

On Sun, Dec 12, 2021 at 6:04 PM Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
wrote:

> On 8/31/21 00:14, Zhihong Yu wrote:
> > Hi,
> > For patch 0002,
> >
> > + s1 = statext_clauselist_selectivity(root, clauses,
> > varRelid,
> > + jointype,
> > sjinfo, rel,
> > +
> > &estimatedclauses, false);
> > +
> > + estimated = (bms_num_members(estimatedclauses) == 1);
> >
> > I took a look at clauselist_apply_dependencies() (called by
> > statext_clauselist_selectivity) where estimatedclauses is modified.
> > Since the caller would not use the returned Selectivity if number of
> > elements in estimatedclauses is greater than 1, I wonder
> > if a parameter can be added to clauselist_apply_dependencies() which
> > indicates early return if the second element is added
> to estimatedclauses.
> >
>
> Hmmm, I'm not sure I understand your point. Are you suggesting there's a
> bug in not updating the bitmap, or would this be an optimization? Can
> you give an example of a query affected by this?
>
> Hi,
My previous comment was from 3 months ago - let me see if I can come up
with an example.

Cheers

>
> regards
>
> --
> Tomas Vondra
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>