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.roua...@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
>>>>>
>> ______
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