Re: Questions about support function and abbreviate
| От | Han Wang |
|---|---|
| Тема | Re: Questions about support function and abbreviate |
| Дата | |
| Msg-id | CADCmNp1dYmPq9rcy5ujx+3zH51d7uCX5iR+5jAJfyhr4pe97BA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Questions about support function and abbreviate (Darafei "Komяpa" Praliaskouski <me@komzpa.net>) |
| Ответы |
Re: Questions about support function and abbreviate
|
| Список | pgsql-hackers |
Hi Darafei,
Thanks for your reply.
However, I still don't get the full picture of this. Let me make my question more clear.
First of all, in the `gistproc.c` of Postgres, it shows that the `abbreviate` attributes should be set before the `abbrev_converter` defined. So I would like to know where to define a `SortSupport` structure with `abbreviate` is `true`.
Secondly, in the support functions of internal data type `Point`, the `abbrev_full_copmarator` just z-order hash the point first like the `abbrev_converter` doing and then compare the hash value. So I don't know the difference between `full_comparator` and `comparator` after `abbrev_converter`.
Best regards,
Han
On Sat, Jun 12, 2021 at 2:55 PM Darafei "Komяpa" Praliaskouski <me@komzpa.net> wrote:
Hello,the abbrev_converter is applied whenever it is defined. The values are sorted using the abbreviated comparator first using the shortened version, and if there is a tie the system asks the real full comparator to resolve it.This article seems to be rather comprehensive: https://brandur.org/sortsupportOn Sat, Jun 12, 2021 at 9:51 AM Han Wang <hanwgeek@gmail.com> wrote:Hi all,I am trying to implement a sort support function for geometry data types in PostGIS with the new feature `SortSupport`. However, I have a question about this.I think it is hardly to apply a sort support function to a complex data type without the `abbrev_converter` to simply the data structure into a single `Datum`. However, I do not know how the system determines when to apply the converter.I appreciate any answers or suggestions. I am looking forward to hearing from you.Best regards,Han--
В списке pgsql-hackers по дате отправления: