hope API for ConnectionID()

[hanchuanchuan]

When I create a connection, I want to get the connection ID, which may have been multiple times.
Is it possible to implement ConnectionID()?
Poor efficiency when using select connection_id() multiple times

Configuration

Go version: go 1.12

Server version: MySQL 5.7.19

Server OS: CentOS7

[methane]

It is impossible in current database/sql design.

[hanchuanchuan]

Thank you for your reply!
Can I do this like this? (#791)

// at `packets.go` `readInitPacket()` 
// connection id [4 bytes]
pos := 1 + bytes.IndexByte(data[1:], 0x00) + 1 + 4
connectionId := int(binary.LittleEndian.Uint32(data[pos-4 : pos]))

Thanks again!

[methane]

I can't understand your question. Could you explain what you want in application?

Note that you don't use this driver directly, but uses database/sql package.
We can't add public API usable from application.

[hanchuanchuan]

Whenever I execute a statement, I want to get the connection id.
The current implementation is

db.Exec("update t1 set c1=1 where id = 1")
// do something...

// get connection_id to use binlog parse
db.Query("select connection_id();")

But I have to get it many times (possibly tens of thousands of times),
so I don't want to go to the database to query the connection id every time.
Thanks!

[methane]

Go golang/go#29835.

[kardianos]

May I ask: why do you want the Connection ID from the driver?

[hanchuanchuan]

I need a Connection ID to resolve the mysql binlog log and it will execute multiple times.

[hanchuanchuan]

Thank you everyone, the problem has been solved!
Upgrade the mysql driver to github.com/go-sql-driver/mysql@v1.4.1.
(I am sorry for the old version that I have been using before. )
All database operations use a uniform method.
When it is found that a new connection is used, it will query the connection ID once.

func (s *session) Raw(sqlStr string) (rows *sql.Rows, err error) {
    // retry 3 times
    for i := 0; i < maxBadConnRetries; i++ {
        rows, err = s.db.DB().Query(sqlStr)
        if err == nil {
            return
        } else {
            log.Error(err)
            if err == mysqlDriver.ErrInvalidConn {
                err = s.initConnection()
                if err != nil {
                    return
                }
            } else {
                return
            }
        }
    }
    return
}

func (s *session) initConnection() (err error) {
    name := "mysql"   

    // retry 3 times
    for i := 0; i < maxBadConnRetries; i++ {
        if err = s.db.Exec(fmt.Sprintf("USE `%s`", name)).Error; err == nil {
            // reset thread id
            s.threadID = 0
            return
        } else {            
            if err != mysqlDriver.ErrInvalidConn {                
                log.Error(err)
                return
            }
        }
    }

    if err != nil {
        log.Error(err)        
    }

    return
}