Re: doc: improve the restriction description of using indexes on REPLICA IDENTITY FULL table.

On Tue, Jul 11, 2023 at 4:54 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> On Mon, Jul 10, 2023 at 2:21 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Mon, Jul 10, 2023 at 7:55 AM Peter Smith <smithpb2250@gmail.com> wrote:
> > >
> > > On Sat, Jul 8, 2023 at 1:49 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > > >
> > > > On Fri, Jul 7, 2023 at 1:36 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > > >
> > > > > I prefer the first suggestion. I've attached the updated patch.
> > > > >
> > > >
> > > > This looks mostly good to me but I think it would be better if we can
> > > > also add the information that the leftmost index column must be a
> > > > non-expression. So, how about: "Candidate indexes must be btree,
> > > > non-partial, and the leftmost index column must be a non-expression
> > > > and reference to a published table column (i.e. cannot consist of only
> > > > expressions)."?
> > >
> > > That part in parentheses ought to say "the index ..." because it is
> > > referring to the full INDEX, not to the leftmost column. I think this
> > > was missed when Sawada-san took my previous suggestion [1].
> > >
> > > IMO it doesn't sound right to say the "index column must be a
> > > non-expression". It is already a non-expression because it is a
> > > column. So I think it would be better to refer to this as an INDEX
> > > "field" instead of an INDEX column. Note that "field" is the same
> > > terminology used in the docs for CREATE INDEX [2].
> > >
> >
> > I thought it would be better to be explicit for this case but I am
> > fine if Sawada-San and you prefer some other way to document it.
> >
>
> I see. How about just moving the parenthesized part to explicitly
> refer only to the leftmost field?
>
> SUGGESTION
> Candidate indexes must be btree, non-partial, and the leftmost index
> field must be a column (not an expression) that references a published
> table column.
>

Yeah, something like that works for me.

--
With Regards,
Amit Kapila.