[PostGIS] #5687: PostgreSQL 17 regression failures with spgist indexes

[PostGIS]

#5687: PostgreSQL 17 regression failures with spgist indexes
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  Reporter:  robe     |      Owner:  robe
      Type:  defect   |     Status:  reopened
  Priority:  blocker  |  Milestone:  PostGIS 3.5.0
 Component:  postgis  |    Version:  3.4.x
Resolution:           |   Keywords:
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Comment (by robe):

 Okay I think I got the issue now what's wrong.

 The postgis_get_full_version_schema() function, tries to find the oid of
 the postgis_full_version() function and it uses, postgresql's
 FuncnameGetCandidates to try to find that schema.  However
 FuncnameGetCandidates function only searches the schemas in the
 search_path for said function.  So since the code wiped out public (the
 most likely location of PostGIS install), it can't find the schema
 anymore.
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5687#comment:7>
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