[postgis-devel] Proposal: Adding buffer parameter to ST_TileEnvelope()

[Yuri Astrakhan]

How should we grow tiles then with regards to the bounds parameter?  I see
two approaches:
* bbox longitude (x) is not clipped unless it grows wider than the bounds,
in which case the result spans the whole bounding box. Latitude (y) is
always clipped.
    PROs: makes it possible to use with geometry columns without any extra
modifications.
    CONs: might cause confusion because the result could be outside of
bounds, and because it might not match geometries across antimeredian.
* bbox grows up to the bounds, and then gets clipped.
    PROs: all generated bboxes are within the bounds, using it as filter
always matches real data in the geometry columns.
    CONs: have to manually extend it across antimeredian if needed.

I'm inclined to go with the first approach, would that be ok?

On Thu, Nov 14, 2019 at 7:58 AM Paul Ramsey <pramsey at cleverelephant.ca>
wrote:

>
>
> On Nov 13, 2019, at 11:35 PM, Yuri Astrakhan <yuriastrakhan at gmail.com>
> wrote:
>
> Rough implementation PR - https://github.com/postgis/postgis/pull/514
>
> I am having some issues with unit tests (too much magic in auto-generated
> code?), so a Postgis guru's help might be needed.
>
> One open concern: extending envelope beyond antimeredian. Is this
> possible? Would a bbox from the tile that overflows to the other side of
> antimeredian match any geometries? For example, given two points - one at
> -179, and the other is at +179 (longitude), would they be found with the
> bbox that goes from -200..-160 ?
>
>
> In geometry they would not match, in geography they would.
>
> P
>
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