remote_url_allow_hosts is checked on very late stage, probably after schema inference

[den-crane]

cat /etc/clickhouse-server/config.d/url.xml
<?xml version="1.0"?>
<yandex>
	<remote_url_allow_hosts></remote_url_allow_hosts>
</yandex>

select * from url('http://google.com', 'TSVRaw');

0 rows in set. Elapsed: 44.475 sec.

Received exception from server (version 22.2.1):
Code: 491. DB::Exception: Received from localhost:9000. DB::Exception:
 URL "http://www.google.com/" is not allowed in configuration file, see <remote_url_allow_hosts>. (UNACCEPTABLE_URL)


select * from url('http://google.com', 'TSVRaw', 'S String');
Elapsed: 0.015 sec.

Received exception from server (version 22.2.1):
Code: 491. DB::Exception: Received from localhost:9000. DB::Exception:
 URL "http://google.com" is not allowed in configuration file, see <remote_url_allow_hosts>. (UNACCEPTABLE_URL)

[den-crane]

remote_url_allow_hosts restricts remote , url , S3, HDFS, DICTIONARY with HTTP source

but not mysql / postgresql / ( I did not check odbc/ Mongodb / Redis / Cassandra )

select * from url('http://127.0.0.1', 'TSVRaw', 'S String');
DB::Exception: URL "http://127.0.0.1" is not allowed in configuration file, see <remote_url_allow_hosts>. (UNACCEPTABLE_URL)



select * from mysql('127.0.0.1:3306', 'dw', 'test', 'u', '123');
Ok.
0 rows in set. Elapsed: 0.019 sec.




SELECT *
FROM mysql('127.0.0.1:9004', 'system', 'one', 'default', '')

Received exception from server (version 22.2.1):
Code: 1000. DB::Exception: Received from localhost:9000. DB::Exception: mysqlxx::BadQuery: Code: 47. DB::Exception: Missing columns: 'TABLE_SCHEMA'

and in config.xml it states <!-- Host should be specified exactly as in URL. The name is checked before DNS resolution.