[postgis-devel] Much slower processing on GEOS 3.9.0 versus 3.8.0 for geodesic area calculation

[Marco Boeringa]

Hi Paul,

Maybe I can put a nail into that GEOS coffin myself. I now attempted to 
reproduce this issue a third time after another restore of the VM from 
backup, but now was really careful to only select the bare minimum in 
Synaptic Package Manager.

As a bare minimum, these were updated:

* libgeos-3.9.0
* libgeos-c1v5
* libgeos-dev

to 3.9.0.

This now ran at *normal* speed, so no slow down compared to 3.8.0.

I want to investigate this further, and see if installing any of the 
other possible upgrades from the UbuntuGIS repository, that Synaptic 
offers once I refresh it, potentially are involved. Will take some time 
to find out though.

Marco

Op 27-4-2021 om 22:46 schreef Paul Ramsey:
> Just to stick a nail in the GEOS-version-affects-geography-area conversation, I took the time to set up two builds (GEOS 3.8 and GEOS 3.9) and swapped between them without changing anything else about the system.
>
> postgis=# select postgis_full_version();
>                                                                                                                                                                            postgis_full_version
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>   POSTGIS="3.2.0dev 3.1.0rc1-162-g46efb9f2d" [EXTENSION] PGSQL="130" GEOS="3.8.3-CAPI-1.13.4" PROJ="8.0.0" GDAL="GDAL 3.2.0, released 2020/10/26" LIBXML="2.9.4" LIBJSON="0.15" LIBPROTOBUF="1.3.3" WAGYU="0.5.0 (Internal)"
>
> postgis=# select sum(st_area(geom::geography)) from va;
>          sum
> --------------------
>   1070124793748.3967
> (1 row)
>
> Time: 1449.551 ms (00:01.450)
>
>
> Then stop the server, change the LD_LIBRARY_PATH to the 3.9 install location and restart.
>
> postgis=# select postgis_full_version();
>                                                                                                                                                                              postgis_full_version
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>   POSTGIS="3.2.0dev 3.1.0rc1-162-g46efb9f2d" [EXTENSION] PGSQL="130" GEOS="3.9.2dev-CAPI-1.14.2" PROJ="8.0.0" GDAL="GDAL 3.2.0, released 2020/10/26" LIBXML="2.9.4" LIBJSON="0.15" LIBPROTOBUF="1.3.3" WAGYU="0.5.0 (Internal)"
>
> postgis=# select sum(st_area(geom::geography)) from va;
>          sum
> --------------------
>   1070124793748.3959
> (1 row)
>
> Time: 1439.969 ms (00:01.440)
>
>
>
> There's no effect to be seen when GEOS version is the only variable in play.
>
> P
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-devel