the process for init_connect = -1 is incompatible with mysql

[seiya-annie]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

in tidb v6.1.0

mysql> SET global init_connect = -1;
Query OK, 0 rows affected (0.01 sec)

mysql> show global variables like 'init_connect';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| init_connect  | -1    |
+---------------+-------+
1 row in set (0.00 sec)

in MySQL 8.0.29
mysql> SET global init_connect = -1;
ERROR 1232 (42000): Incorrect argument type to variable 'init_connect'

2. What did you expect to see? (Required)

compatible with MySQL

3. What did you see instead (Required)

tidb don't report error for invalid value type

4. What is your TiDB version? (Required)

Git Commit Hash: 1a89dec
Git Branch: heads/refs/tags/v6.1.0
UTC Build Time: 2022-06-05 05:15:11

[Defined2014]

We will transfer datum to str before validation ref link. So we need to pass datum param for SetGlobalSysVar instead of string to fix this issue.

[likzn]

SysVar has TypeFlag with each system environment. And we also can get input type with v.Expr.Eval(chunk.Row{}) in Datum. What about adding a check with type limit to resolve this issue.

tidb/executor/set.go

Lines 299 to 314 in 9a77892

	func (e *SetExecutor) getVarValue(v *expression.VarAssignment, sysVar *variable.SysVar) (value string, err error) {
	if v.IsDefault {
	// To set a SESSION variable to the GLOBAL value or a GLOBAL value
	// to the compiled-in MySQL default value, use the DEFAULT keyword.
	// See http://dev.mysql.com/doc/refman/5.7/en/set-statement.html
	if sysVar != nil {
	return sysVar.Value, nil
	}
	return variable.GetGlobalSystemVar(e.ctx.GetSessionVars(), v.Name)
	}
	nativeVal, err := v.Expr.Eval(chunk.Row{})
	if err != nil || nativeVal.IsNull() {
	return "", err
	}
	return nativeVal.ToString()
	}

[morgo]

There is an easier fix here without having to modify the sysvar framework. Specify a Validation function for InitConnect, and in that func try and parse the new val. If it fails, return the error message that MySQL is returning here and then the SET will fail.