No enough privileges for autovacuum worker

Hi everyone,

Every minute, I see the following error message in my server logs:

2021-03-23 13:00:07.564 MSK [60828]-[]-[]-[autovacuum worker]-[42501]-[(at)] ERROR: permission denied for schema dict at character 34
2021-03-23 13:00:07.564 MSK [60828]-[]-[]-[autovacuum worker]-[42501]-[(at)] QUERY:
SELECT array_to_string(dict.trigrams_array($1), ' ')::tsvector;

2021-03-23 13:00:07.564 MSK [60828]-[]-[]-[autovacuum worker]-[42501]-[(at)] CONTEXT: SQL function "trigrams_vector" during inlining
automatic analyze of table "fpdb.fpbackup.fp_vpn_data_2021w12"

It seems that something related to autovacuum does not have enough
privileges to do some particular work, but I have no idea to what
and/or to whom I should grant privileges to fix this problem.

log setting from postgresql.conf:
log_line_prefix = '%m [%p]-[%h]-[%a]-[%b]-[%e]-[%u(at)%d] '

PostgreSQL version 13.

Any ideas?

--
Best regards,

Andrey Sychev

andrey(dot)sychev(at)cifrasoft(dot)com