ST_SafeSubdivide

[strk]

As reported in #4636 the ST_Subdivide function may degrade input, due to the necessity to add vertices at exact grid intersection point, and being sometimes unable to do so.

A ST_SafeSubdivide function may instead limit itself to split at existing vertices.

[komzpa]

If you understand how to change the algorithm behind Subdivide to achieve this, how about just replacing ST_Subdivide?

[strk]

Because the idea in this ticket is to use existing vertices, which would be a behavioural change from what ST_Subdivide does (it ensures to split areas exactly on the given grid).

If we can get a fully robust ST_Subdivide then I'd be in favour of dropping this ticket and do that instead.

[robe]

I hate the name ST_Safe anything for PostGIS packaged functions.

It's okay for user-defined functions stuff, but safe demands having ST_Safe for everything. Please STOP NOW before you initiate a SAFE movement.

[strk]

ST_BestEffortSubdivide ?

[robe]

Better Effort bu ST_Subdivide still sounds best. Throw another arg in there.

[strk]

Spatialite has a TopoGeo_SubdivideLines function that takes both maxlength and maxvertices arguments, splitting on whatever is reached first. Could be an idea to copy that interface. See ​https://www.gaia-gis.it/gaia-sins/spatialite-sql-5.1.0.html

[strk]

The "fully respecting Topology consistency" part of the spatialite function is what I was after for this ticket.