left/right/substring from mysql table reports error

[RangerWolf]

Describe the bug
Could not use left or right or substring when selecting data from mysql directly

How to reproduce

• Version: 19.11.2
• SQL that could run with error

-- Exception msg for below sql : 
-- Code: 1000. DB::Exception: Received from clickhouse-server:9000. DB::Exception: mysqlxx::BadQuery: Operand should contain 1 column(s)
select 
            `id`
from mysql('host:port', 'database', 'tablename', 'username', 'password')
where 1=1 and left(stat_datetime, 10)='2019-08-07'  and advertiser_id = '12345'

• SQL that runs OK

select 
	`id`
from mysql('host:port', 'database', 'tablename', 'username', 'password')
where 1=1 and advertiser_id = '12345'

Expected behavior
Both SQL should run OK

[alexey-milovidov]

@dimarub2000 Please try to reproduce this issue.

[dimarub2000]

Reproduced the issue, trying to find the problem.
when select * from mysql('localhost:3306', 'test', 'kek', 'dsrub', 'kek') where id=123 and 1=1;
mysql gets SELECT `s`, `id` FROM `test`.`kek` WHERE (`id` = 123) AND (1 = 1)

when select * from mysql('localhost:3306', 'test', 'kek', 'dsrub', 'kek') where left(s, 2) = 'ke'
mysql gets SELECT `s`, `id` FROM `test`.`kek`

when select * from mysql('localhost:3306', 'test', 'kek', 'dsrub', 'kek') where left(s, 2) = 'ke' and id=123 and 1=1;
mysql gets SELECT `s`, `id` FROM `test`.`kek` WHERE (`id` = 123, 1 = 1)

why substring() function is not sent to mysql but is processed localy?