[postgis-devel] Validity flag

Oliver Courtin olivier.courtin at oslandia.com
Mon Feb 29 05:15:24 PST 2016

Le 29 févr. 2016 à 14:00, Sandro Santilli a écrit :

> On Mon, Feb 29, 2016 at 12:45:38PM +0100, Oliver Courtin wrote:
>> With only the _valid_ one , if we are sure that geometry is valid, 
>> we could skip the check validity in SFCGAL (or other backend),
>> and if we not sure (i.e unknown or not valid), 
>> we have to do the check validity backend side.
> Why check if it's already checked and invalid ?
> You could just say it's invalid, right away, and
> suggest to use ST_MakeValid.
> BTW, ST_MakeValid checks for validity as its first thing,
> making it slow when the input is already known as being
> invalid. It would then also benefit from knowing _invalid_
> from the start.
> And ST_Simplify (for example) could set _invalid_ flag when
> returning collapsed lines (structurally invalid).

I understand what you mean, Sandro, but:

- We don't have that much flags still available 

- On userland indeed we allow invalid geometry to be stored, 
  but only with the ST_MakeValid stuff, or equivalent, in mind.

  I can't figure a reason to encourage keeping invalid data on a long term.


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