OK, I found the cause of the unaccent dictionary problem, and a workaround.
It's not the vacuumdb version, not the unaccent version, and it's not even a pg_upgrade problem: I get this error also with PG 9.4.18 running on the old cluster, with both the 10.5 vacuumdb and the 9.4.18 vacuumdb, and I get the same error in both.
And it's not strictly a vacuumdb problem, though vacuumdb triggers it.
Here's a very minimal test case, unrelated to my DB, that you ought to be able to reproduce:
SET search_path = "$user"; SELECT public.unaccent('fóö');
SET
ERROR: text search dictionary "unaccent" does not exist
and here's a workaround:
SET search_path = "$user"; SELECT public.unaccent(tsdict.oid, 'fóö')
FROM pg_catalog.pg_ts_dict tsdict WHERE dictname='unaccent';
SET
unaccent
----------
foo
(1 row)
The workaround avoids the OID lookup of the dictionary ... that lookup (in the single-argument unaccent function) is done by unqualified name:
dictOid = get_ts_dict_oid(stringToQualifiedNameList("unaccent"), false);
and that fails if the search path doesn't include public.
So the workaround for my vacuumdb/function-index problem is to give unaccent the OID of the text search dictionary, so that the search path isn't in play:
CREATE OR REPLACE FUNCTION public.semantic_normalize(title text)
RETURNS text
LANGUAGE sql
IMMUTABLE STRICT
AS $function$
SELECT lower(public.unaccent(16603, btrim(regexp_replace($1, '\s+', ' ', 'g'), ' "')))
$function$;
and that makes vacuumdb -z work in both 9.4.18 and 10.5, and makes ./analyze_new_cluster.sh complete without problems.
The proper fix is, I suppose, to make the single-argument unaccent function explicitly look up the dictionary in the same schema as the function itself is in.
