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

On 28.02.2024 13:07, jian he wrote:
> On Wed, Feb 28, 2024 at 12:19 PM Andrei Lepikhov
> <a.lepikhov@postgrespro.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).

I suggest describing our feature in array.sgml and mentioning a GUC there.

We can describe a GUC in config.sgml.

>> 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.

Maybe like that:

It also considers the way to generate a path using BitmapScan indexes, 
converting the transformed expression into expressions separated by "OR" 
operations, and if it turns out to be the best and finally selects the 
best one.

-- 
Regards,
Alena Rybakina
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company