Re: POC, WIP: OR-clause support for indexes

On Wed, Feb 28, 2024 at 12:19 PM Andrei Lepikhov
<a(dot)lepikhov(at)postgrespro(dot)ru> wrote:
>
> On 26/2/2024 11:10, Alena Rybakina wrote:
> > On 24.02.2024 14:28, jian he wrote:
> >> Hi.
> >> I wrote the first draft patch of the documentation.
> >> it's under the section: Planner Method Configuration
> >> (runtime-config-query.html)
> >> but this feature's main meat is in src/backend/parser/parse_expr.c
> >> so it may be slightly inconsistent, as mentioned by others.
> >>
> >> You can further furnish it.
> >
> > Thank you for your work. I found a few spelling mistakes - I fixed this
> > and added some information about generating a partial index plan. I
> > attached it.
> Thanks Jian and Alena,
> It is a good start for the documentation. But I think the runtime-config
> section needs only a condensed description of a feature underlying the
> GUC. The explanations in this section look a bit awkward.
> Having looked through the documentation for a better place for a
> detailed explanation, I found array.sgml as a candidate. Also, we have
> the parser's short overview section. I'm unsure about the best place but
> it is better when the server config section.

doc/src/sgml/array.sgml corresponds to
https://www.postgresql.org/docs/current/arrays.html.
this GUC is related to parser|optimzier.
adding a GUC to array.sgml seems strange. (I think).

> 2. We should describe the second part of the feature, where the
> optimiser can split an array to fit the optimal BitmapOr scan path.

we can add a sentence explaining that:
it may not do the expression transformation when the original
expression can be utilized by index mechanism.
I am not sure how to rephrase it.