[postgis-devel] Validity flag

Daniel Baston dbaston at gmail.com
Fri Mar 4 05:58:10 PST 2016

I like the suggestion to add an optional set of extra flags at the end of
the geometry, as a nice backwards-compatible way to store extra information
when we need the ability.  But it seems like overkill for the current
situation, where we do have flags available in the current structure.  Can
we not get 99% of the benefits (avoid repeatedly testing geometries known
to be valid) by storing the single "valid / unknown" flag in the current

On unrelated note, do we need to further quality what we mean by "valid" ?
Is SFCGAL validity always the same as GEOS validity ?


On Mon, Feb 29, 2016 at 1:54 PM, Sandro Santilli <strk at keybit.net> wrote:

> On Mon, Feb 29, 2016 at 09:23:13AM -0800, Paul Ramsey wrote:
> > I have another (better?) option:
> > Use one of the existing bits be an "extra-8-bytes" flag. That way we
> > can have lots of extra info if we want, in cases where fluff isn't an
> > issue, and without ruining alignment.
> > Thanks Hugo for the idea,
> Yes, "extra-8-bytes" is the alternative.
> But Hugo idea could be limited to "1-byte" (with another "extend" bit
> in case we need more) w/out affecting alignment.
> So I guess it all depends on how much we want to reduce on-disk size
> (assuming a single byte would not be padded to next 8-bytes boundary
> on disk write...).
> --strk;
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