[postgis-tickets] [PostGIS] #4890: ST_Transform large slow down from upgrade to 3.1.1 from 2.4

[PostGIS]

#4890: ST_Transform large slow down from upgrade to 3.1.1 from 2.4
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  Reporter:  SAbernethy  |      Owner:  pramsey
      Type:  defect      |     Status:  new
  Priority:  blocker     |  Milestone:  PostGIS 3.1.2
 Component:  postgis     |    Version:  3.1.x
Resolution:              |   Keywords:
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Comment (by pramsey):

 The results of postgis_full_version() would be interesting to me.

 When we moved into the proj 6 and higher series we got the new
 "transformation chain" calculations which are much more expensive to set
 up when turning an EPSG->EPSG transformation into a transformation object
 ready to process coordinates.

 PostGIS caches the transformation object per-statement when it gets it, so
 over a 1M vertex object, the new set-up cost is not really visible.
 However, over 1M **separate statements** that set up cost will not be
 amortized at all.

 A workaround is to try and change your data flow so that you can do your
 transforms in one query, instead of millions of separate queries. (You
 also might look at st_buffer(geography) as an alternative to your current,
 or really just using cartographic markers instead of building out concrete
 circles, but none of that has anything to do with projection overhead.)

 First thing though, your full versions so we can see what the proj version
 difference is.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4890#comment:4>
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