Fix variable formatting for ErrTruncateWrongValue

[alapha23]

System variables of mysql could be 50 characters at most according to the document, which is group_replication_flow_control_certifier_threshold.

Modify the ErrTruncateWrongValue so that system variable names will not be truncated in the error message.

We could presume error message will not exceed mysql limits, as there are longer error messages as the official document suggests, e.g.

Error number: 1041; Symbol: ER_OUT_OF_RESOURCES; SQLSTATE: HY000
Message: Out of memory; check if mysqld or some other process uses all available memory; if not, you may have to use 'ulimit' to allow mysqld to use more memory or you can add more swap space 

Please correct me if I misunderstood anything. Thank you in advance!

[shenli]

@alapha23 Could you post the error message from MySQL in that case?

[lysu]

@alapha23 maybe also take a PR in tidb repo and add a unit test for

variable.ErrTruncatedWrongValue.GenWithStackByArgs("group_replication_flow_control_certifier_threshold", "1")

to make CI green and make tidb's PR referenece this one

test parser from tidb can use https://github.com/pingcap/parser/blob/master/README.md's method.

[alapha23]

@shenli @lysu
So this parser is relevant to this pr on tidb

As you might have seen from circleci that mysql system variable validate_password_mixed_case_count_value is truncated because of the error message formatting,

FAIL: set_test.go:283: testSuite.TestValidateSetVar
set_test.go:526:
    tk.MustQuery("show warnings").Check(testutil.RowsWithSep("|", "Warning|1292|Truncated incorrect validate_password_mixed_case_count value: '-1'"))
/go/src/github.com/pingcap/tidb/util/testkit/testkit.go:55:
    res.c.Assert(resBuff.String(), check.Equals, needBuff.String(), res.comment)
... obtained string = "[Warning 1292 Truncated incorrect validate_password_mixed_case_cou value: '-1']\n"
... expected string = "[Warning 1292 Truncated incorrect validate_password_mixed_case_count value: '-1']\n"
... sql:show warnings, args:[]

I presume we are able to know the error message is decent or not by check ci of the tidb pr I mentioned above.

What do you think?
Thank you in advance!

[alapha23]

@lysu Thank you for suggesting the readme. I will take a careful look and follow the steps.

[tiancaiamao]

@lysu PTAL

[lysu]

@shenli I have checked error message from MySQL in that case is same with this PR's result

[lysu]

@alapha23 let me take a look..

[alapha23]

@lysu
Thank you for the comment!
I encountered errors after switching the parser.
The parameter collate seems to differ between expected string and obtained string.

For example, make dev under tidb would have

expr_to_pb_test.go:327:
    c.Assert(string(js), Equals, jsons[funcNames[i]], Commentf("%v\n", funcNames[i]))
... obtained string = "{\"tp\":10000,\"children\":[{\"tp\":201,\"val\":\"gAAAAAAAAAE=\",\"sig\":0,\"field_type\":{\"tp\":5,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":46,\"charset\":\"\"}},{\"tp\":201,\"val\":\"gAAAAAAAAAI=\",\"sig\":0,\"field_type\":{\"tp\":5,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":46,\"charset\":\"\"}}],\"sig\":200,\"field_type\":{\"tp\":5,\"flag\":128,\"flen\":-1,\"decimal\":-1,\"collate\":63,\"charset\":\"binary\"}}"
... expected string = "{\"tp\":10000,\"children\":[{\"tp\":201,\"val\":\"gAAAAAAAAAE=\",\"sig\":0,\"field_type\":{\"tp\":5,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":83,\"charset\":\"\"}},{\"tp\":201,\"val\":\"gAAAAAAAAAI=\",\"sig\":0,\"field_type\":{\"tp\":5,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":83,\"charset\":\"\"}}],\"sig\":200,\"field_type\":{\"tp\":5,\"flag\":128,\"flen\":-1,\"decimal\":-1,\"collate\":63,\"charset\":\"binary\"}}"
... plus

There are quite a few errors of this kind and you could refer to the whole output message in log.txt

Thank you very much!

[lysu]

@alapha23 hi, it seem pingcap/tidb#8227 CI passed

what means switching the parser ?

[alapha23]

@lysu
CI passed because I removed the system variable which is longer than the limit. In that case I was using pingcap/parser

For switching the parser, I mean I was trying to use this modified parser for further testing.
Above error happened when using this modified parser.

What do you think of the error message?
Sorry for the trouble. And thank you for your consistent help.

[lysu]

LGTM

[lysu]

@tiancaiamao @yu34po PTAL

[zz-jason]

LGTM