[postgis-tickets] [PostGIS] #3569: ST_CollectionHomogenize sometimes returns reference to argument

[PostGIS]

#3569: ST_CollectionHomogenize sometimes returns reference to argument
---------------------+---------------------------
 Reporter:  dbaston  |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  high     |  Milestone:  PostGIS 2.2.3
Component:  postgis  |    Version:  2.2.x
 Keywords:           |
---------------------+---------------------------
 I noticed this situation when digging into a question posted on Stack
 Exchange: http://gis.stackexchange.com/questions/195915/weird-behavior-
 with-st-clusterwithin

 That question itself isn't relevant here, but the some of the test data
 can be used to make a reproducible (for me) test case of the problem:

 {{{
 CREATE TABLE cluster_inputs (
     name text,
     geom geometry
 );

 CREATE TABLE cluster (
     geom geometry
 );

 INSERT INTO cluster (geom) VALUES
 ('010700002031BF0D000100000001030000000100000005000000713D0AD76D4D11C1A4703D9AE5955941713D0AD76D4D11C1A4703D9A94965941713D0AD77D4211C1A4703D9A94965941713D0AD77D4211C1A4703D9AE5955941713D0AD76D4D11C1A4703D9AE5955941');
 INSERT INTO cluster (geom) VALUES
 ('010700002031BF0D00010000000103000000010000000D0000009A9999998B3211C114AE47F13D965941295C8FC2863211C1A4703D5A569659418FC2F528D33011C1EC51B84E5A9659417B14AE47B62F11C1B81E851B5A965941295C8FC2BC2F11C18FC2F5F85D96594114AE47E10D2C11C1295C8FE26F965941EC51B81EF32B11C1666666D6699659417B14AE47D12C11C1F6285CFF139659418FC2F528BA2F11C1F6285C7F14965941B81E85EBBE2F11C11F85EB01279659415C8FC2F5DB2F11C1D7A3702D2C965941F6285C8F2F3011C15C8FC235309659419A9999998B3211C114AE47F13D965941');


 INSERT INTO cluster_inputs (name, geom) VALUES ('a',
 '010300002031BF0D000100000005000000713D0AD76D4D11C1A4703D9AE5955941713D0AD76D4D11C1A4703D9A94965941713D0AD77D4211C1A4703D9A94965941713D0AD77D4211C1A4703D9AE5955941713D0AD76D4D11C1A4703D9AE5955941');
 INSERT INTO cluster_inputs (name, geom) VALUES ('b',
 '010300002031BF0D00010000000D0000009A9999998B3211C114AE47F13D965941295C8FC2863211C1A4703D5A569659418FC2F528D33011C1EC51B84E5A9659417B14AE47B62F11C1B81E851B5A965941295C8FC2BC2F11C18FC2F5F85D96594114AE47E10D2C11C1295C8FE26F965941EC51B81EF32B11C1666666D6699659417B14AE47D12C11C1F6285CFF139659418FC2F528BA2F11C1F6285C7F14965941B81E85EBBE2F11C11F85EB01279659415C8FC2F5DB2F11C1D7A3702D2C965941F6285C8F2F3011C15C8FC235309659419A9999998B3211C114AE47F13D965941');

 }}}

 For me, running the following query then produces an error:

 {{{
 SELECT
   cluster_inputs.name,
   ST_Intersects(ST_CollectionHomogenize(cluster.geom),
 cluster_inputs.geom)
 FROM cluster_inputs, cluster
 ORDER BY name;

 ERROR:  First argument geometry could not be converted to GEOS:
 IllegalArgumentException: Points of LinearRing do not form a closed
 linestring
 }}}

 which suggests a memory issue.  The problem can be resolved by wrapping
 the return of {{{lwgeom_homogenize}}} with an {{{lwgeom_clone_deep}}},
 which seems to confirm this.  Since the return of {{{lwgeom_homogenize}}}
 references portions of its argument, and {{{ST_CollectionHomogenize}}}
 releases the serialized input before serializing the output, we seem to
 have a problem.

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3569>
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