[postgis-devel] Z-order implementation from PostgreSQL

[Han Wang]

Hi Darafei,

Thanks for your reply.

I noticed that it is a well-done Hillbert implementation. However, in the
SoC project, I need to complete another Z-order one for further research
and performance testing.
So maybe it is a good way to refer to your Hillbert implementation.

Best regards,
Han

On Wed, Jun 2, 2021 at 11:11 PM Darafei "Komяpa" Praliaskouski <
me at komzpa.net> wrote:

> Hello,
>
> The correct way to implement that would be to borrow the compare function
> that already exists in postgis (
> https://github.com/postgis/postgis/blob/master/liblwgeom/gserialized.c#L313:5)
> and already sorts everything in a nice Hilbert curve. All of the type
> punning is already there.
>
> On Wed, Jun 2, 2021 at 6:04 PM Han Wang <hanwgeek at gmail.com> wrote:
>
>> Hi all,
>>
>> I am currently working on the GSoC project of `*Implementating a
>> pre-sorting methods before GiST index building*` and now try to borrow
>> some ideas from z-order implementation
>> <https://github.com/postgres/postgres/blob/master/src/backend/access/gist/gistproc.c#L1761>
>> in Postgres.
>> I am wondering, however, if I should use lower level postgres functions
>> like `*point_zorder_internal
>> <https://github.com/postgres/postgres/blob/master/src/backend/access/gist/gistproc.c#L1576>*`
>> and `*ieee_float32_to_uint32*
>> <https://github.com/postgres/postgres/blob/master/src/backend/access/gist/gistproc.c#L1604>`
>> and data structure like `*BOX
>> <https://github.com/postgres/postgres/blob/master/src/include/utils/geo_decls.h#L140>*
>> `.
>> What's more, I don't know if it is necessary to implement a util function
>> `*ieee_float32_to_uint32*` in lwgeom.
>>
>> I appreciate your ideas and suggestions. Feel free to talk to me.
>>
>> Best regards,
>> Han
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>>
>
>
> --
> Darafei "Komяpa" Praliaskouski
> OSM BY Team - http://openstreetmap.by/
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