[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:  pramsey
      Type:  defect       |     Status:  new
  Priority:  medium       |  Milestone:  PostGIS 2.4.0
 Component:  postgis      |    Version:  2.3.x
Resolution:               |   Keywords:
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Comment (by robe):

 Unfortunately short of mucking with the system catalogs I don't think so.

 PostgreSQL doesn't have a create or replace agg like it does for functions
 and in 2.4 we marked most aggs parallel safe so they need drop/recreate
 for the changes to take effect.

 and alter aggregate doesn't give us much power except to rename aggs.

 https://www.postgresql.org/docs/9.6/static/sql-alteraggregate.html

 What you could do, if you are on PostgreSQL 9.5 or lower these extra
 clauses aren't in there so in theory you shouldn't need to drop, so you
 could just remark out the DROP AGG .. CREATE AGG in the extension scripts.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3821#comment:1>
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