Cannot suppress SET character_set_client=utf8?

[jploski]

I'm trying to use query rewrite rules to get rid of "SET character_set_client=utf8" that is being sent to my (Clickhouse-using-MySQL-protocol) backend by the MySQL Workbench client (which makes any connection attempt fail). Using ProxySQL version 2.2.0-72-ge14accd, codename Truls.

I added this rule in an attempt to neutralize all SET statatements:

INSERT INTO mysql_query_rules (active, match_pattern, replace_pattern) VALUES (1,"^SET .*$", "select * from system.parts where 1=0");
LOAD MYSQL QUERY RULES TO RUNTIME;

If I use the mysql CLI client, I can see in stats.stats_mysql_query_rules that the rule works when I execute the statement "SET character_set_client=utf8" directly through it. But when I try connecting through the MySQL Workbench, the rule does not fire, rather, the statement is passed through to the backend Clickhouse, where I of course get the error:

executeQuery: Code: 62. DB::Exception: Syntax error: failed at position 26 ('utf8'): utf8. Expected one of: TRUE, FALSE, literal, NULL, number, Bool, true, false, string literal. (SYNTAX_ERROR) (version 21.12.2.17 (official build)) (from 127.0.0.1:41456) (in query: SET character_set_client=utf8)...

(The reason why I'm not using the Clickhouse module of ProxySQL is that it reliably crashes ProxySQL - but that's another story.)

[jploski]

Note, there is also an open issue in Clickhouse regarding all the incompatibilities that bother MySQL clients: ClickHouse/ClickHouse#9336

[jploski]

FWIW, I got it to connect by recompiling ProxySQL with the following patch (which is obviously not a good idea to include in any official code base, just a proof-of-concept)

https://gist.github.com/jploski/0ce2a9b797f0055085827e687f28f3e8