Add connection attributes

[Daemonxiao]

Description

This PR refers to #350, #1241.

Connection attributes are key-value pairs that application programs can pass to the server at connect time.

Users can now define connection attributes by adding "&connectionAttributes=attr1:value1,attr2:value2" in the DSN string.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[Daemonxiao]

@dveeden PTAL. This PR refers to yours #350.

[dveeden]

Looks good on first glance, I'll have a more in depth look later.

[dveeden]

What's the issue with MariaDB?

[dveeden]

I tried this:

package main

import (
	"database/sql"
	"fmt"

	_ "github.com/go-sql-driver/mysql"
)

func main() {
	db, err := sql.Open("mysql", "root:msandbox@tcp(127.0.0.1:8032)/test?connectionAttributes=foo:bar,foobar:")
	if err != nil {
		panic(err)
	}
	defer db.Close()

	r, err := db.Query("SELECT ATTR_NAME, ATTR_VALUE FROM performance_schema.session_connect_attrs WHERE PROCESSLIST_ID=CONNECTION_ID()")
	if err != nil {
		panic(err)
	}
	for r.Next() {
		var attrName, attrValue any
		err := r.Scan(&attrName, &attrValue)
		if err != nil {
			panic(err)
		}
		if attrValue == nil {
			attrValue = "NULL"
		}
		fmt.Printf("%-20s - %-30s\n", attrName, attrValue)
	}
}

Output is as expected, both the driver set attributes and the user supplied ones

$ go run connattr.go 
_client_name         - GO-MySQL-Driver               
_os                  - linux                         
_platform            - amd64                         
foo                  - bar                           
foobar               - NULL                

[Daemonxiao]

MariaDB does not resolve connection attributes.
I will find more information in the MariaDB protocol.

MariaDB root@127.0.0.1:(none)> SELECT * FROM performance_schema.session_connect_attrs WHERE processlist_id=CONNECTION_ID();
                            ->
+----------------+-----------+------------+------------------+
| PROCESSLIST_ID | ATTR_NAME | ATTR_VALUE | ORDINAL_POSITION |
+----------------+-----------+------------+------------------+
+----------------+-----------+------------+------------------+

[dveeden]

I can indeed confirm issues with MariaDB 11.0.0-preview and connection attributes. This is with both a MariaDB client and with a MySQL client.

Wireshark shows that connection attributes are sent by both clients, but not shown by the server.

This doesn't match with their docs: https://mariadb.com/kb/en/performance-schema-session_connect_attrs-table/

[dveeden]

It might be possible to set _pid to os.Getpid(). Not sure if that would be meaningful with goroutines etc and/or if this would be useful.

[Daemonxiao]

@dveeden OK, I will add _pid. Maybe someone needs it.

[dveeden]

I reported the issue with MariaDB here: https://jira.mariadb.org/browse/MDEV-30570

[dveeden]

I reported the issue with MariaDB here: https://jira.mariadb.org/browse/MDEV-30570

@vuvova responded in the ticket with a embarrassingly simple conclusion: performance schema isn't enabled. The difference between MariaDB and MySQL is that MariaDB doesn't enable this by default.

Let's see if we can enable this on MariaDB for the CI here and not exclude MariaDB from the tests.

This should be as easy as adding performance_schema to

mysql/.github/workflows/test.yml

Lines 78 to 84 in 4591e42

	my-cnf: |
	innodb_log_file_size=256MB
	innodb_buffer_pool_size=512MB
	max_allowed_packet=16MB
	; TestConcurrent fails if max_connections is too large
	max_connections=50
	local_infile=1

[Daemonxiao]

I reported the issue with MariaDB here: https://jira.mariadb.org/browse/MDEV-30570

@vuvova responded in the ticket with a embarrassingly simple conclusion: performance schema isn't enabled. The difference between MariaDB and MySQL is that MariaDB doesn't enable this by default.

Let's see if we can enable this on MariaDB for the CI here and not exclude MariaDB from the tests.

This should be as easy as adding performance_schema to

mysql/.github/workflows/test.yml

Lines 78 to 84 in 4591e42

	my-cnf: |
	innodb_log_file_size=256MB
	innodb_buffer_pool_size=512MB
	max_allowed_packet=16MB
	; TestConcurrent fails if max_connections is too large
	max_connections=50
	local_infile=1

@dveeden Thank you for your continued dedication. I have modified pr according to your suggestion, and the MariaDB tests all pass. That's great. 😊

[methane]

@Daemonxiao Please check my last commit (5ba21b7).
Would you add yourself to AUTHORS?

[methane]

@Daemonxiao Please make a PR to add yourself to AUTHOR file.

[Daemonxiao]

@Daemonxiao Please make a PR to add yourself to AUTHOR file.

@methane I have done this in #1459. PTAL :)