Trying to use sqlx to connect to Apache Doris

[ChunHou20c]

Recently I am trying out connecting to Apache Doris using mysql protocol. While using mysql client, the connection works fine, however when trying to connect to Apache Doris using sqlx I get an error:

ERROR 1105 (HY000): errCode = 2, detailMessage = Set statement does't support non-constant expr.

It seems like sqlx is trying to set some sqlx options using concatenation, after investigating the by logging the debug message this is what I find out:

TRACE sqlx::query > summary="SET sql_mode=(SELECT CONCAT(@@sql_mode, ',NO_ENGINE_SUBSTITUTION')),time_zone='+00:00',NAMES …" db.statement="\n\nSET\n  sql_mode =(\n    SELECT\n      CONCAT(@ @sql_mode, ',NO_ENGINE_SUBSTITUTION')\n  ),\n  time_zone = '+00:00',\n  NAMES utf8 COLLATE utf8_unicode_ci;\n" rows_affected=0 rows_returned=0 elapsed=63.366745ms
 TRACE sqlx::query > summary="SET sql_mode=(SELECT CONCAT(@@sql_mode, ',NO_ENGINE_SUBSTITUTION')),time_zone='+00:00',NAMES …" db.statement="\n\nSET\n  sql_mode =(\n    SELECT\n      CONCAT(@ @sql_mode, ',NO_ENGINE_SUBSTITUTION')\n  ),\n  time_zone = '+00:00',\n  NAMES utf8 COLLATE utf8_unicode_ci;\n" rows_affected=0 rows_returned=0 elapsed=61.703453ms
thread 'tokio-runtime-worker' panicked at src/data_importer.rs:148:54:
Database(MySqlDatabaseError { code: Some("HY000"), number: 1105, message: "errCode = 2, detailMessage = Set statement does't support non-constant expr." })

And I am able to reproduce this error in Apache Doris using this query:

MySQL [(none)]> set sql_mode=(SELECT CONCAT(@@sql_mode,'NO_ENGINE_SUBSTITUTION'));
ERROR 1105 (HY000): errCode = 2, detailMessage = Set statement does't support non-constant expr.

So it appear that Doris doesn't support setting the sql mode by concatenating the values, and for mysql client it just doesn't set any value.

My question is, what will actually happen if we don't set the value in sqlx? And is it possible to disable the set of the sql_option when establishing the connection in sqlx? I do see the sql_options is set using concat in the connect function in https://github.com/launchbadge/sqlx/blob/main/sqlx-mysql/src/options/connect.rs.