[postgis-users] Cut extent box2d into small regular boxes, and iterate through each box of features

[Shaozhong SHI]

Hi, Lars,

Thanks for suggestions.

Your execute parallel is very interesting.  Are there explanations or a
documentation or a guide available?

Regards,

David

On Mon, 28 Mar 2022 at 11:09, Lars Aksel Opsahl <Lars.Opsahl at nibio.no>
wrote:

> >From: postgis-users <postgis-users-bounces at lists.osgeo.org> on behalf of
> Shaozhong SHI <shishaozhong at gmail.com>Sent: Monday, March 28, 2022 11:42
> AMTo: PostGIS Users Discussion <postgis-users at lists.osgeo.org>Subject:
> Re: [postgis-users] Cut extent box2d into small regular boxes, and iterate
> through each box of features
> >Hi, Lars,
> >
> >Would the following alternative work?
> >
> >In PostGIS, one can group by geometry.  Based on this information, can
> grid be generated?  so that grid with 0 features can be skipped.
> >
>
> Hi
>
> In our cases this would not solve our problems, because grid cells with
> zero content does not cause any big performance issue problems, but we do
> not need them so it's nice to get reed of them.
>
> But I think it's easier to have a complete grids coverage and instead vary
> cell size based on content. If you have a set of 10 mill polygons and and
> you make a grid so you can process them in parallel  what's important is
> that each job has about the same needs related to memory and CPU, and this
> can be done by setting for instance a max a value for number of features pr
> cell. (You can here also count number points in each polygon but that takes
> more time and you can not base the grid cell creation on indexes)
>
> Lars
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