Re: Making Vars outer-join aware

Hello and sorry for the big delay in reply!

On 04.05.2023 15:22, Tom Lane wrote:
> AFAICS the change you propose would serve only to mask bugs.

Yes, it's a bad decision.

> Under what circumstances would you be trying to inject INDEX_VAR
> into a nullingrel set? Only outer-join relids should ever appear there.

The thing is that i don't try to push INDEX_VAR into a nullingrel set at all,
i just try to replace the existing rt_index that equals to INDEX_VAR in Var nodes with
the defined positive indexes by using ChangeVarNodes_walker() function call. It checks
if the nullingrel contains the existing rt_index and does it need to be updated too.
It calls bms_is_member() for that, but the last immediately throws an error
if the value to be checked is negative like INDEX_VAR.

But we are not trying to corrupt the existing nullingrel with this bad index,
so it doesn't seem like an serious error.
And this index certainly cannot be a member of the Bitmapset.

Therefore it also seems better and more logical to me in the case of an index that
cannot possibly be a member of the Bitmapset, immediately return false.

Here is a patch like that.

With the best regards,

--
Anton A. Melnikov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company