Re: Removing unneeded self joins

On Thu, Jul 15, 2021 at 7:49 AM Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>
wrote:

> On 6/7/21 13:49, Hywel Carver wrote:
> > On Mon, Jul 5, 2021 at 2:20 PM Andrey Lepikhov
> > <a(dot)lepikhov(at)postgrespro(dot)ru <mailto:a(dot)lepikhov(at)postgrespro(dot)ru>> wrote:
> > Looking through the email chain, a previous version of this patch added
> > ~0.6% to planning time in the worst case tested - does that meet the
> > "essentially free" requirement?
> I think these tests weren't full coverage of possible use cases. It will
> depend on a number of relations in the query. For the JOIN of
> partitioned tables, for example, the overhead could grow. But in the
> context of overall planning time this overhead will be small till the
> large number of relations.
> Also, we made this feature optional to solve possible problems.
> Rebased on 768ea9bcf9
>
> --
> regards,
> Andrey Lepikhov
> Postgres Professional
>
Hi,

bq. We can proof the uniqueness

proof -> prove

1. Collect all mergejoinable join quals looks like a.x = b.x

quals looks like -> quals which look like

For update_ec_sources(), the variable cc is not used.

Cheers