[mapserver-dev] Proposal/request to implement FlatGeobuf as built-in format
Jeff McKenna
jmckenna at gatewaygeomatics.com
Wed May 18 13:09:48 PDT 2022
Thanks for the positive support Lars, your testing feedback is
important, and merry Christmas ha.
Regarding your question, please see the section "3.3 Limitations" of the
RFC which is supposed to handle your question.
-jeff
On 2022-05-18 4:07 p.m., Lars Schylberg wrote:
> Thanks, Björn and Jeff for the effort to do this.I am eager to start
> testing soon.As a user I feel that Santa is coming early this year.
>
> I also have one question.Is the native FlatGeobuf driver doing the
> reading without checks, like "VERIFY_BUFFERS" "NO" that you can set in
> the OGR driver?
>
> My inofficial +1
>
> Lars Schylberg
>
> Den 2022-05-18 kl. 17:09, skrev Steve Lime:
>> Nice work all - esp. Björn. Evan has a good point that sounds like it
>> could be addressed. Couple of comments:
>>
>> 1. I'd like to see a security impact section added just so it's clear
>> that it has been thought about. For example, what is behavior if a
>> corrupt, invalid or truncated file is accessed.
>> 2. Does the flatgeobuf directory contain only code specific to
>> MapServer or is there a mix of custom code and 3rd party code? If
>> there is 3rd party code could there be a discussion about how that
>> should be maintained over time?
>> 3. Are things pinned to a particular version of flatbuf - I assume
>> yes and that should be noted.
>> 4. I'm assuming there are no MapScript issues - might be nice to
>> explicitly state that.
>>
>> --Steve
>>
>> On Wed, May 18, 2022 at 6:38 AM Even Rouault
>> <even.rouault at spatialys.com> wrote:
>>
>> I'm 0 on this. While this is always nice to see a perf
>> improvement, I'm
>> somewhat concerned by the duplication of code between MapServer
>> and GDAL.
>>
>> And from a purely technical point of view, one of my worry is that
>> symbol clashes might occur between GDAL and MapServer on the
>> common code
>> they share in the FlatGeobuf and flatbuffers C++ namespaces. If the
>> implementations are not kept in sync (and that will necessarily
>> happen
>> at some point because we cannot control which GDAL version is used by
>> MapServer), weird things (crashes) could possibly happen at
>> runtime (or
>> at build time if doing static builds). That worry could be solved by
>> possibly having a mapserver:: prefix in front of those namespace
>> names
>> (can be done with some #define trickery. See
>> https://github.com/OSGeo/PROJ/blob/9f89c7288e44c64ba234a299b1d5528a54d9d61e/include/proj/util.hpp#L104
>>
>> for potential inspiration)
>>
>> The interesting take-away from my perspective is that the OGR
>> overhead
>> for FlatGeobuf is only 5 ms, but 13 ms for Shapefile. So one
>> interpretation would be that there's some inefficiency in the OGR
>> Shapefile driver vs the native MapServer provider.
>>
>> Even
>>
>> Le 17/05/2022 à 15:19, Jeff McKenna a écrit :
>> > Update: Björn has completed the effort (which now includes several
>> > msautotests) and we've created an RFC (137) for the native
>> FlatGeobuf
>> > support: https://mapserver.org/development/rfc/ms-rfc-137.html
>> >
>> > I therefore motion to include FlatGeobuf as a native MapServer
>> driver,
>> > per RFC 137, and maintained by Björn Harrtell.
>> >
>> > starting with my +1
>> >
>> > Some other interesting updates:
>> >
>> > - great to see changes here made through testing benefiting so many
>> > other projects
>> >
>> > - here is an updated benchmark result (that is mentioned in the
>> RFC) :
>> >
>> >
>> > FlatGeobuf (native) 0.008s
>> > Shapefile (native) 0.010s
>> > FlatGeobuf (OGR) 0.013s
>> > Shapefile (OGR) 0.023s
>> > GeoPackage (OGR) 0.042s
>> > SpatiaLite (OGR) 0.045s
>> > PostGIS (native) 0.053s
>> > GeoJSON (OGR) 0.089s
>> >
>> > (that was with yesterday's main, GDAL 3.4.3, with MS4W on Windows)
>> >
>> > - with all this testing done, and the existing FlatGeobuf
>> > documentation effort, it will be very easy to add this to the main
>> > documentation now...
>> >
>> > Thanks,
>> >
>> >
>> > -Björn & Jeff
>> >
>> >
>> >
>> >
>> >
>> > On 2022-04-27 3:07 p.m., Jeff McKenna wrote:
>> >> Great point Even, here is an updated result:
>> >>
>> >> Shapefile 0.011s
>> >> FlatGeobuf 0.014s
>> >> Shapefile (OGR) 0.024s
>> >> GeoPackage 0.042s
>> >> SpatiaLite 0.045s
>> >> PostGIS 0.053s
>> >> GeoJSON 0.089s
>> >>
>> >>
>> >> -jeff
>> >>
>> >>
>> >>
>> >>
>> >> On 2022-04-27 2:09 p.m., Even Rouault wrote:
>> >>> Jeff,
>> >>>
>> >>> as a data point, perhaps you could enhance your bench with
>> >>> shapefiles through OGR ? It would be interesting to have a
>> sense of
>> >>> the OGR overhead (that will be the same for any OGR supported
>> >>> datasource) to have an idea if it is really worth the effort
>> to have
>> >>> a native FlatGeobuf provider for MapServer w.r.t going through
>> OGR
>> >>> (it is hard to beat shapefile, and the current difference between
>> >>> shapefile and flatgeobuf is small)
>> >>>
>> >>> Even
>> >>>
>> >>> Le 26/04/2022 à 12:57, Jeff McKenna a écrit :
>> >>>> (to followup from our chat on IRC yesterday)
>> >>>>
>> >>>> To clarify: this would be a new native format in MapServer,
>> such as
>> >>>> Shapefile or PostGIS, and the goal would be to not connect to
>> >>>> FlatGeobuf through OGR, but instead directly, such as:
>> >>>>
>> >>>> DATA countries.fgb
>> >>>>
>> >>>> instead of:
>> >>>>
>> >>>> CONNECTIONTYPE OGR
>> >>>> CONNECTION "countries.fgb"
>> >>>> DATA "countries"
>> >>>>
>> >>>> This should improve the performance even more. And it will
>> be easy
>> >>>> to update the documentation, as the existing files just need
>> to be
>> >>>> updated (see the new page at
>> >>>> https://mapserver.org/input/vector/flatgeobuf.html )
>> >>>>
>> >>>> Great plan Björn! I look forward to your Pull Request, ha, and
>> >>>> will tackle the documentation changes for you.
>> >>>>
>> >>>> This is also great news for MapServer, and will give us some
>> nice
>> >>>> publicity.
>> >>>>
>> >>>> Thanks so much!
>> >>>>
>> >>>> -jeff
>> >>>>
>> >>>>
>> >>>>
>> >>>> On 2022-04-25 5:57 p.m., Björn Harrtell wrote:
>> >>>>> Hi mapserver devs!
>> >>>>>
>> >>>>> I got interested in the subject because of the tests made
>> recently
>> >>>>> by Jeff that shows the potential of the format. I believe it
>> >>>>> should be possible to get significant additional performance
>> out
>> >>>>> of FlatGeobuf in MapServer if it was built in just like
>> Shapefile
>> >>>>> support is.
>> >>>>>
>> >>>>> FlatGeobuf C++ implementation is rather small, doesn't
>> require any
>> >>>>> dependencies, and I don't expect it to require any invasive
>> >>>>> changes to existing code.
>> >>>>>
>> >>>>> Would love to get started on this ASAP, if there are no
>> >>>>> objections. :)
>> >>>>>
>> >>>>> Regards,
>> >>>>> Björn Harrtell
>> >>>>>
>> >> ______
>> > _______________________________________________
>> > MapServer-dev mailing list
>> > MapServer-dev at lists.osgeo.org
>> > https://lists.osgeo.org/mailman/listinfo/mapserver-dev
>>
>> --
>> http://www.spatialys.com
>> My software is free, but my time generally not.
>>
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