Got he following after changing log_level from 4 => 3 and ejabberdctl reload_config:
2019-01-04 10:32:15.561 [error] <0.3680.0>@ejabberd_hooks:safe_apply:384 Hook config_reloaded crashed when running ejabberd_rdbms:config_reloaded/0:
** Reason = {error,badarg,[{ets,select_count,[],[sql_pool,[{{sql_pool,'$1','_'},[{'==','$1',{const,<<"example.com">>}}],[true]}]]},{ejabberd_sql_sup,reload,[{file,"src/ejabberd_sql_sup.erl"},{line,76}],1},{lists,foreach,[{file,"lists.erl"},{line,1338}],2},{ejabb
erd_hooks,safe_apply,[{file,"src/ejabberd_hooks.erl"},{line,380}],4},{ejabberd_hooks,run1,[{file,"src/ejabberd_hooks.erl"},{line,329}],3},{ejabberd_ctl,call_command,[{file,"src/ejabberd_ctl.erl"},{line,351}],4},{ejabberd_ctl,try_call_command,[{file,"src/ejabb
erd_ctl.erl"},{line,320}],4},{ejabberd_ctl,process2,[{file,"src/ejabberd_ctl.erl"},{line,270}],4}]}
** Arguments = []
Every SQL config is commented:
root@server:/etc/ejabberd# grep sql_pool ejabberd.yml
## auth_method: sql
## sql_type: pgsql
## sql_server: "server"
## sql_database: "database"
## sql_username: "username"
## sql_password: "password"
## sql_port: 1234
## pgsql_users_number_estimate: true
## sql_type: sqlite
## sql_database: "/path/to/database.db"
## sql_pool_size: 10
## sql_keepalive_interval: undefined