[postgis-tickets] [PostGIS] #3821: Don't drop st_union when updating postgis extension to 2.4

[PostGIS]

#3821: Don't drop st_union when updating postgis extension to 2.4
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  Reporter:  nextstopsun  |      Owner:  robe
      Type:  defect       |     Status:  closed
  Priority:  medium       |  Milestone:  PostGIS 2.4.0
 Component:  postgis      |    Version:  2.3.x
Resolution:  fixed        |   Keywords:
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Comment (by robe):

 dmkaplan2000,

 Sadly as mentioned about going from 2.4 to 2.5.2 DOES REQUIRE a DROP
 AGGREGATE.  You don't even want to edit this script as that would put your
 system in an unstable state if you do not drop the aggregate.

 What was discussed above was when we changed midstream in a development
 cycle, marking ST_Union as parallel safe -- that change can be done with a
 catalog update and even if you don't not a huge deal -- just means your
 ST_Union couldn't use paralle constructs.


 Unfortunately going from 2.4 -> 2.5 we changed the underlying helper
 functions so not a trivial catalog update.
 A PostgreSQL team member (Andrew aka (RhodiumToad) ), heard our pains and
 blessed us with an ALTER AGGREGATE SQL construct in PostgreSQL 12 which we
 can use for most cases.  So if running PostgreSQL 12 or above we  use
 ALTER AGGREGATE to make changes.  That doesn't come till 3.0 though.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3821#comment:26>
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