postgis_raster upgrade fails on PG16

[rdunklau]

postgis_raster upgrade fails on PG16 with the error message:

ERROR: attempt to redefine parameter "postgis.gdal_datapath"

This comes from the implementation of postgis_guc_find_option for PG16, which passes a random address instead of the GUC name.

Here is a real simple patch fixing that:

diff --git a/libpgcommon/lwgeom_pg.c b/libpgcommon/lwgeom_pg.c
index 6af4bea39..f7f848adc 100644
--- a/libpgcommon/lwgeom_pg.c
+++ b/libpgcommon/lwgeom_pg.c
@@ -521,7 +521,7 @@ postgis_guc_find_option(const char *name)
         * the name field is first in config_generic.
         */
 #if POSTGIS_PGSQL_VERSION >= 160
-       res = (struct config_generic **) find_option((void *) &key, false, true, ERROR);
+       res = (struct config_generic **) find_option((void *) name, false, true, ERROR);
 #else
        res = (struct config_generic **) bsearch((void *) &key,
                 (void *) get_guc_variables(),
-- 
2.43.0

One should probably remove the cast to (void *) while at it

[Regina Obe <lr@…>]

In bfc8cd7/git:

Fix for postgis raster PG 16 guc
References #5648 for PostGIS 3.5.0
patch from Ronan Dunklau

[Regina Obe <lr@…>]

In b0943c0/git:

Fix for postgis raster PG 16 guc
References #5648 for PostGIS 3.4.2
patch from Ronan Dunklau

[Regina Obe <lr@…>]

In d27577a0/git:

Fix for postgis raster PG 16 guc
Closes #5648 for PostGIS 3.3.6
patch from Ronan Dunklau

[Regina Obe <lr@…>]

In 18e7f66c/git:

Revert #5648 fix
Causing regression failures on PG16 and PG17
References #5648 and #5650

[robe]

I rolled back this change on master, cause it was breaking our upgrade tests and several raster tests (with can't change guc) as noted in #5650. The upgrade tests failing are more mysterious to me.

I also left a dangling variable key, but that was a separate issue which fixing that did not fix the underlying issue in #5650.

I'm still checking to see if it's our tests at fault here, cause looking at the definition in PostgreSQL code

struct config_generic *
find_option(const char *name, bool create_placeholders, bool skip_errors,
			int elevel)

This code should have worked

[Regina Obe <lr@…>]

In 13d4f48/git:

Revert #5648 fix
Causing regression failures on PG16 and PG17
References #5648 and #5650

[Regina Obe <lr@…>]

In 66b10e5/git:

Remove from NEWS #5648. References #5648 since we reverted.