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

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.

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Kind Regards,
Peter Smith.
Fujitsu Australia