I have generated nominatim database before and never faced such an issue.
Please tell me which "setup.php" command generates the "search_name_0" and such tables?
Full error output is:
-bash-4.2$ ./utils/setup.php --index --threads 8 --osm2pgsql-cache 24000
nominatim version 2.5.1
Starting indexing rank (0 to 4) using 8 threads
Starting rank 0
Done 0 in 0 @ 0.000000 per second - FINISHED
Starting rank 1
Done 0 in 0 @ 0.000000 per second - FINISHED
Starting rank 2
index_placex: UPDATE failed: ERROR: relation "search_name_0" does not exist
LINE 1: DELETE from search_name_0 WHERE place_id = in_place_id
^
QUERY: DELETE from search_name_0 WHERE place_id = in_place_id
CONTEXT: PL/pgSQL function deletesearchname(integer,bigint) line 1260 at SQL statement
PL/pgSQL function placex_update() line 75 at assignment
index_placex: UPDATE failed: ERROR: relation "search_name_0" does not exist
LINE 1: DELETE from search_name_0 WHERE place_id = in_place_id
^
QUERY: DELETE from search_name_0 WHERE place_id = in_place_id
CONTEXT: PL/pgSQL function deletesearchname(integer,bigint) line 1260 at SQL statement
PL/pgSQL function placex_update() line 75 at assignment
index_placex: UPDATE failed: ERROR: relation "search_name_0" does not exist
LINE 1: DELETE from search_name_0 WHERE place_id = in_place_id
^
QUERY: DELETE from search_name_0 WHERE place_id = in_place_id
CONTEXT: PL/pgSQL function deletesearchname(integer,bigint) line 1260 at SQL statement
PL/pgSQL function placex_update() line 75 at assignment
index_placex: UPDATE failed: ERROR: relation "search_name_0" does not exist
LINE 1: DELETE from search_name_0 WHERE place_id = in_place_id
^
QUERY: DELETE from search_name_0 WHERE place_id = in_place_id
CONTEXT: PL/pgSQL function deletesearchname(integer,bigint) line 1260 at SQL statement
PL/pgSQL function placex_update() line 75 at assignment
ERROR: Error executing external command: /srv/Nominatim-2.5.1/nominatim/nominatim -i -d nominatim -P 5432 -t 8 -R 4
Error executing external command: /srv/Nominatim-2.5.1/nominatim/nominatim -i -d nominatim -P 5432 -t 8 -R 4
-bash-4.2$
It took some time to figure out but it happens when your "create-partition-tables" part of setup fails.
Restarting it will fail to re-create the tables. I had to manually remove all partition tables and then restarted the setup with "create-partition-tables" key to solve this!