Hi Richard > BTW, since commit cb8e50a4a, we've chosen not to wrap a non-var > expression if it contains Vars/PHVs of the pulled-up subquery and does > not contain non-strict constructs. I wonder if we can apply the same > optimization from this patch to non-var expressions: for a LATERAL > subquery, if a non-var expression contains Vars/PHVs of the > lowest_nullable_relids and does not contain non-strict constructs, it >could also escape being wrapped. Any thoughts? agree , The path tested and looks good to me,In addition, can the test case have a multi-layer nested subquery(maybe) ?
Thanks On Wed, Nov 27, 2024 at 4:46 PM Richard Guo <guofengli...@gmail.com> wrote: > On Fri, Nov 22, 2024 at 5:08 AM Dmitry Dolgov <9erthali...@gmail.com> > wrote: > > The patch looks good to me, the implementation is concise and clear. I > can't > > imagine any visible overhead due to storing lowest_nullable_relids in > this > > context. The only nitpick I have is about this commentary: > > > > /* > > * Simple Vars always escape being wrapped, unless they are > > * lateral references to something outside the subquery being > > - * pulled up. (Even then, we could omit the PlaceHolderVar if > > - * the referenced rel is under the same lowest outer join, but > > - * it doesn't seem worth the trouble to check that.) > > + * pulled up and the referenced rel is not under the same > > + * lowest outer join. > > */ > > > > It mentions "lowest outer join", as in the original version of the text. > Would > > it be more precise to mention nullable side of the outer join as well? > > Thank you for your review. > > I ended up using 'under the same lowest nulling outer join' to > keep consistent with the wording used elsewhere. Please see the > updated patch attached. > > BTW, since commit cb8e50a4a, we've chosen not to wrap a non-var > expression if it contains Vars/PHVs of the pulled-up subquery and does > not contain non-strict constructs. I wonder if we can apply the same > optimization from this patch to non-var expressions: for a LATERAL > subquery, if a non-var expression contains Vars/PHVs of the > lowest_nullable_relids and does not contain non-strict constructs, it > could also escape being wrapped. Any thoughts? > > Thanks > Richard >
