[postgis-users] 回复： PostGIS crash on ST_ConcaveHull

[耳辰]

Hi Imre,
Thanks very much and I will try ST_AlphaShape later.
As an alternative way, I back port the ST_ConcaveHull implementation based on pgplsql which used for lower GEOS version. It’s working and may loss performance. 
Looking forward to the bug fix of the issue.
Regards,
Zhen
------------------------------------------------------------------
发件人：Imre Samu <pella.samu at gmail.com>
发送时间：2023年8月18日(星期五) 22:39
收件人：陈振(耳辰) <erchen.cz at alibaba-inc.com>; PostGIS Users Discussion <postgis-users at lists.osgeo.org>
抄　送：宋震(凡玺) <songzhen.sz at alibaba-inc.com>; 谢炯 <xiejiong.xj at alibaba-inc.com>
主　题：Re: [postgis-users] PostGIS crash on ST_ConcaveHull
> Any comment is welcomed.
Hi Zhen,
I've recently tested your example with the "postgis/postgis:15-master" Docker image
[GEOS version: 3.13.0dev-CAPI-1.18.0 + PostGIS version: 3.5.0dev 3.4.0rc1-21-g7faeed1d4], 
and it appears that it crashes as well [1].
However, I found that the CGAL-based alternative ST_AlphaShape is working without issues. [1]+[2] 
postgres=# select ST_AlphaShape('MULTIPOINT ((113.56577197798602 22.80081530883069),(113.565723279387 22.800815316487014),(113.56571548761124 22.80081531771092),(113.56571548780202 22.800815317674463),(113.56577197817877 22.8008153088047),(113.56577197798602 22.80081530883069))'::geometry, 0.75 );
 st_alphashape 
---------------------------------------------------
 010300000001000000070000006288BBAE34645C404AB48F3B02CD364065E369CF34645C4097728A3B02CD36405D9CAB9B35645C405F90693B02CD364059D1AB9B35645C40CC73693B02CD364065E369CF34645C4097728A3B02CD3640D3B
CBBAE34645C40348C8F3B02CD36406288BBAE34645C404AB48F3B02CD3640
(1 row)
[1]
tested with "postgis/postgis:15-master" https://github.com/postgis/docker-postgis <https://github.com/postgis/docker-postgis >
 POSTGIS="3.5.0dev 3.4.0rc1-21-g7faeed1d4" [EXTENSION] PGSQL="150"
GEOS="3.13.0dev-CAPI-1.18.0" SFCGAL="SFCGAL 1.5.0, CGAL 5.6.1, BOOST 1.74.0" PROJ="9.3.0 NETWORK_ENABLED=OFF
 URL_ENDPOINT=https://cdn.proj.org <https://cdn.proj.org > USER_WRITABLE_DIRECTORY=/var/lib/postgresql/.local/share/proj 
 DATABASE_PATH=/usr/local/share/proj/proj.db" LIBXML="2.9.10" LIBJSON="0.15" LIBPROTOBUF="1.3.3" WAGYU="0.5.0
 (Internal)" TOPOLOGY
[2] https://postgis.net/docs/en/ST_AlphaShape.html <https://postgis.net/docs/en/ST_AlphaShape.html >
This function effectively computes a concave hull of a geometry in a similar way to ST_ConcaveHull, but uses CGAL and a different algorithm.
Availability: 3.3.0 - requires SFCGAL >= 1.4.1. ; This method needs SFCGAL backend.
Regards,
 Imre
耳辰 <erchen.cz at alibaba-inc.com <mailto:erchen.cz at alibaba-inc.com >> ezt írta (időpont: 2023. aug. 18., P, 15:05):
Hi guys,
I met a postgis crash when tried to use ST_ConvaveHull function with a multipoint, in postgis 3.3.2 and Geos 3.11.2 :
select ST_ConcaveHull('MULTIPOINT ((113.56577197798602 22.80081530883069),(113.565723279387 22.800815316487014),(113.56571548761124 22.80081531771092),(113.56571548780202 22.800815317674463),(113.56577197817877 22.8008153088047),(113.56577197798602 22.80081530883069))', 0.75);
The crash stack are listed:
#0 0x0000ffff84e02210 in geos::triangulate::tri::Tri::getIndex(geos::triangulate::tri::Tri const*) const () from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#1 0x0000ffff84ce74c0 in geos::algorithm::hull::HullTriangulation::nextBorderTri(geos::algorithm::hull::HullTri*) ()
 from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#2 0x0000ffff84ce7698 in geos::algorithm::hull::HullTriangulation::traceBoundary(geos::triangulate::tri::TriList<geos::algorithm::hull::HullTri>&) ()
 from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#3 0x0000ffff84ce79d4 in geos::algorithm::hull::HullTriangulation::traceBoundaryPolygon(geos::triangulate::tri::TriList<geos::algorithm::hull::HullTri>&, geos::geom::GeometryFactory const*) ()
 from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#4 0x0000ffff84ce1f28 in geos::algorithm::hull::ConcaveHull::toGeometry(geos::triangulate::tri::TriList<geos::algorithm::hull::HullTri>&, geos::geom::GeometryFactory const*) () from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#5 0x0000ffff84ce29d4 in geos::algorithm::hull::ConcaveHull::getHull() ()
 from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2 <http://erchen.cz/pgsql15/lib/libgeos.so.3.11.2 >
#6 0x0000ffff8e54818c in GEOSConcaveHull_r ()
 from /home/erchen.cz/pgsql15/lib/libgeos_c.so.1 <http://erchen.cz/pgsql15/lib/libgeos_c.so.1 >
….
It seemed that geos was failed to triangulate the multipoint and then crashed … Is this a bug of geos?
Any comment is welcomed.
Regards,
Zhen
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