[postgis-devel] ST_AsGeobuf

[Björn Harrtell]

2016-09-12 10:46 GMT+02:00 Paul Norman <penorman at mac.com>:

> On 9/12/2016 12:59 AM, Björn Harrtell wrote:
>
>> Hi devs,
>>
>> I've been working on a new output format function called ST_AsGeobuf
>> these last months. Its purpose is to serialize full query output into the
>> binary format Geobuf containing both geometry and attributes. The
>> implementation is tracked by:
>>
>> https://trac.osgeo.org/postgis/ticket/3599
>> https://git.osgeo.org/gogs/postgis/postgis/pulls/4 or alternatively
>> https://github.com/bjornharrtell/postgis/tree/asgeobuf5
>>
>> Geobuf is a binary format specified by Mapbox that can represent similar
>> data and structure as GeoJSON but is more compact and is faster encode and
>> decode. You can read more about Geobuf at https://github.com/mapbox/geob
>> uf which also serves as the reference implementation to decode at a
>> browser client side.
>>
>> Geobuf is in turn based on Googles protobuf standard which I think is
>> similar to a binary XML. My implementation uses the general purpose library
>> protobuf-c to simplify the encoding.
>>
>> I hope to be able use this work as a base to also implement support for
>> vector tiles as specified by Mapbox which is also based on protobuf.
>>
>> I think the implementation is ready for review and testing. If you have
>> any interest in Geobuf or vector tiles output support I'd appreciate review
>> and/or test result feedback.
>>
>>
> The MapBox geobuf page states "Note that the encoding schema is not stable
> yet". Is it premature to put this in PostGIS?
>

Subjective, I think. I think Mapbox just want to disclaim backwards
compatibility in the eventual next major version. Obviously I find it
useful right now and do think it can be for others too. If needed, PostGIS
could support both the current spec and future ones by parameterization, or
drop support if deemed obsolete.

As far as I know, Mapbox want to evolve the spec so that it can support
encoding/decoding as a stream, but there is no telling when/if that work
will be completed.

And as a final observation, if TWKB could be accepted I think Geobuf should
be. :)

/Björn

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