[postgis-users] PostGIS crash on ST_ConcaveHull

[耳辰]

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

#1  0x0000ffff84ce74c0 in geos::algorithm::hull::HullTriangulation::nextBorderTri(geos::algorithm::hull::HullTri*) ()

  from /home/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

#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

#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

#5  0x0000ffff84ce29d4 in geos::algorithm::hull::ConcaveHull::getHull() ()

  from /home/erchen.cz/pgsql15/lib/libgeos.so.3.11.2

#6  0x0000ffff8e54818c in GEOSConcaveHull_r ()

  from /home/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

[Imre Samu]

> 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

  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 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

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

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[Paul Ramsey]

Thanks, yes a crash is a bug. I have confirmed it exists in GEOS, and filed an issue

https://github.com/libgeos/geos/issues/946

P

[耳辰]

Many thanks,

zhen

陈振 阿里巴巴 电话：057128223456-83773183 邮箱：erch...@alibaba-inc.com 地址：北京-北京-金辉大厦 33F-086 阿里巴巴 企业主页

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------------------------------------------------------------------
发件人：Paul Ramsey<pra...@cleverelephant.ca>
日　期：2023年08月18日 23:12:14
收件人：耳辰<erch...@alibaba-inc.com>; PostGIS Users Discussion<postgi...@lists.osgeo.org>
抄　送：宋震(凡玺)<songz...@alibaba-inc.com>; 谢炯<xieji...@alibaba-inc.com>
主　题：Re: [postgis-users] 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...@gmail.com>

发送时间：2023年8月18日(星期五) 22:39

收件人：陈振(耳辰) <erch...@alibaba-inc.com>; PostGIS Users Discussion <postgi...@lists.osgeo.org>

抄　送：宋震(凡玺) <songz...@alibaba-inc.com>; 谢炯 <xieji...@alibaba-inc.com>

主　题：Re: [postgis-users] PostGIS crash on ST_ConcaveHull