[postgis-tickets] [PostGIS] #3570: Reduce memory usage in ST_ClusterWithin / ST_ClusterDBSCAN

[PostGIS]

#3570: Reduce memory usage in ST_ClusterWithin / ST_ClusterDBSCAN
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 Reporter:  dbaston      |      Owner:  dbaston
     Type:  enhancement  |     Status:  new
 Priority:  medium       |  Milestone:  PostGIS 2.3.0
Component:  postgis      |    Version:  2.2.x
 Keywords:               |
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 The {{{make_strtree}}} function in {{{lwgeom_geos_cluster.c}}} prepares a
 GEOS STRTree of LWGEOM pointers.  To store the LWGEOMs in the STRTree, it
 has to provide {{{GEOSSTRtree_insert}}} with a GEOS geometry whose
 envelope corresponds to the envelope of the LWGEOM.  It's currently doing
 this with {{{GBOX2GEOS}}}, which produces a rectangular GEOS Polygon.
 Since this geometry is never used directly -- it's basically a container
 for an envelope -- this should be replaced with either a GEOS Point or a
 two-point GEOS LineString, depending on the LWGEOM that's being stored in
 the tree.

 This will reduce a significant memory overhead, particularly when
 clustering functions are used on point data sets.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3570>
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