Hi Tom,
Tom Lane <tgl@sss.pgh.pa.us> 于2026年3月21日周六 04:26写道：
>
> I wrote:
> > At the very least we need to add comments, but I wonder if we
> > don't actually need an Assert that ChangeVarNodesWalkExpression
> > is not invoked directly on a Query. It would have done the
> > right thing before this patch, but now it won't. That's an
> > okay tradeoff for fixing the bare-Var case, but not documenting
> > what you did is not okay.
>
> After further contemplation I've decided that an Assert would be
> wrong, because it's not impossible that a callback would want
> to invoke this on a sub-Query --- for instance, if it wanted to
> short-circuit ChangeVarNodes's processing of a SubLink node,
> it would need to do that. The key point is that if we do see a
> Query node here, we will treat it as a sub-query not a top-level
> query, which also justifies skipping the work that
> ChangeVarNodesExtended does on a top-level Query. So we just
> need a comment explaining that. I'm thinking about the attached.
>
> (BTW, by this reasoning the previous implementation of
> ChangeVarNodesWalkExpression was doubly wrong, since it would
> have done the wrong thing at a Query node as well as a Var node.)
Thanks for pointing this out. The attached looks good to me.
Do you have some advice about that the same qual is present
twice in the plan, see [1].
Should we do something in restrict_infos_logically_equal().
Please take a look.
--
Thanks,
Tender Wang
