[PostGIS] #5823: PostgreSQL 18 no longer compiles against postgis

[PostGIS]

#5823: PostgreSQL 18 no longer compiles against postgis
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 Reporter:  robe     |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 3.6.0
Component:  postgis  |    Version:  master
 Keywords:           |
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 Debbies compile of postgis started failing on

 https://debbie.postgis.net/view/PostGIS/job/PostGIS_Regress_PGDEV_Weekly/23896/consoleFull

 which happened after change in postgresql


 {{{
 Commit 5983a4cffc31640fda6643f10146a5b72b203eaa by drowley

 Introduce CompactAttribute array in TupleDesc, take 2

 The new compact_attrs array stores a few select fields from
 FormData_pg_attribute in a more compact way, using only 16 bytes per
 column instead of the 104 bytes that FormData_pg_attribute uses.  Using
 CompactAttribute allows performance-critical operations such as tuple
 deformation to be performed without looking at the FormData_pg_attribute
 element in TupleDesc which means fewer cacheline accesses.

 For some workloads, tuple deformation can be the most CPU intensive part
 of processing the query.  Some testing with 16 columns on a table
 where the first column is variable length showed around a 10% increase in
 transactions per second for an OLAP type query performing aggregation on
 the 16th column.  However, in certain cases, the increases were much
 higher, up to ~25% on one AMD Zen4 machine.

 This also makes pg_attribute.attcacheoff redundant.  A follow-on commit
 will remove it, thus shrinking the FormData_pg_attribute struct by 4
 bytes.

 Author: David Rowley
 Reviewed-by: Andres Freund, Victor Yegorov
 Discussion:
 https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com
 }}}
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5823>
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