mysql memory leak because of prepare statements

Issue description

I'm not sure if this is a bug in mysql or driver but I have a simple script that just simply call prepare statement and close them. when the script is done I expect db to release memory allocated because of this prepared statement but allocated memory won't release. After running script i get following result as part of running show global status like '%com_stmt%':

Com_stmt_prepare: 300
Com_stmt_close: 300

and memory usage reports following output: query:

SELECT SUBSTRING_INDEX(event_name,'/',2) AS
                                            code_area, FORMAT_BYTES(SUM(current_alloc))
                                         AS current_alloc
FROM sys.x$memory_global_by_current_bytes
GROUP BY SUBSTRING_INDEX(event_name,'/',2)
ORDER BY SUM(current_alloc) DESC;

output:

memory/performance_schema,220.66 MiB
memory/innodb,192.54 MiB
memory/sql,9.67 MiB
memory/mysys,8.60 MiB
memory/temptable,1.00 MiB
memory/mysqld_openssl,121.38 KiB
memory/mysqlx,3.38 KiB
memory/vio,1.16 KiB
memory/myisam, 728 bytes
memory/csv, 120 bytes
memory/blackhole, 120 bytes

while allocated memory on mysql process is more than 6G

Example code

package main

import (
    "database/sql"
    "fmt"
    "log"
    "strings"

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

func main() {
    dsn := "root:root@tcp(localhost:3306)/tes_db"
    db, err := sql.Open("mysql", dsn)
    if err != nil {
        log.Fatalf("Failed to connect to the database: %v", err)
    }
    defer db.Close()

    question := "? ,"
    qlen := 0
    for i := 0; i < 300; i++ {
        if i < 40 {
            for i := 0; i < 1000; i++ {
                question += "? ,"
            }
        }
        query := "SELECT " + strings.TrimRight(question, ",")
        qlen += len(query)
        _, err := db.Prepare(query)
        if err != nil {
            log.Fatalf("Failed to prepare statement %d: %v", i, err)
        }

        fmt.Printf("Prepared statement %d\n", i)
    }

    fmt.Println("Finished preparing statements", qlen/1024/1024)
}

In this code I'm not closing statements. If I close them the memory leak is gone but if command is just finished memory leak is still there although mysql reports them as closed.

Error log

If you have an error log, please paste it here.

Configuration

Driver version (or git SHA): v1.8.1

Go version: run go version 1.22

Server version: mysql 9.0.1, 8.0.37

Server OS: E.g. macos (mysql was on docker)

go-sql-driver / mysql