Incorrect datetime value for column of type time.Time when inserted by BulkInserter

[kayoch1n]

Describe the bug
I was trying to use the bulk insertion feature mentioned by docs. The bug arises when one needs to insert a time.Time value.

The BulkInserter in go-zero is using a function writeValue, in which Time.String() is being used to convert a time.Time variable into string. Time.String() returns a format like "2006-01-02 15:04:05.999999999 -0700 MST" that is not accepted by MySQL, which i believe is the cause of this bug.

func writeValue(buf *strings.Builder, arg any) {
    // ...
    case time.Time:
		buf.WriteByte('\'')
		buf.WriteString(v.String())
		buf.WriteByte('\'')

To Reproduce
I wrote a unittest case to reproduce this problem

CREATE TABLE 
    IF NOT EXISTS greet (
        `id` INT NOT NULL AUTO_INCREMENT,
        `name` VARCHAR(64) NOT NULL,
        `released_at` DATETIME NOT NULL,
        PRIMARY KEY(`id`)
    ) ENGINE=InnoDB;

func TestBulkInsert(t *testing.T) {
	conn := sqlx.NewMysql("root:MySQL@2026@tcp(127.0.0.1:3306)/gzgreet?parseTime=true&loc=Asia%2FShanghai&charset=utf8mb4,utf8")

	inserter, _ := sqlx.NewBulkInserter(
		conn, 
		fmt.Sprintf("INSERT INTO `greet` (%s) VALUES (?, ?)", greetRowsExpectAutoSet),
	)
	defer inserter.Flush()

	require.NoError(t, inserter.Insert("bob", time.Now()))

	done := make(chan error)
	inserter.SetResultHandler(func(r sql.Result, err error) {
		done <- err
	})
	result := <- done
	assert.NoError(t, result)
}

The error is

Incorrect datetime value: '2026-03-28 17:26:54.88284 +0800 CST m=+0.007881418' for column 'released_at' at row 1

The SQL generated by bulk inserter

INSERT INTO `greet` (`name`,`released_at`) VALUES ('bob', '2026-03-28 17:26:54.88284 +0800 CST m=+0.007881418')

{"@timestamp":"2026-03-28T17:26:55.999+08:00","caller":"sqlx/stmt.go:274","content":"sql exec: INSERT INTO `greet` (`name`,`released_at`) VALUES ('bob', '2026-03-28 17:26:54.88284 +0800 CST m=+0.007881418')","duration":"24.3ms","level":"info"}
{"@timestamp":"2026-03-28T17:26:55.999+08:00","caller":"sqlx/utils.go:147","content":"stmt: INSERT INTO `greet` (`name`,`released_at`) VALUES ('bob', '2026-03-28 17:26:54.88284 +0800 CST m=+0.007881418'), error: Error 1292 (22007): Incorrect datetime value: '2026-03-28 17:26:54.88284 +0800 CST m=+0.007881418' for column 'released_at' at row 1","level":"error"}

Expected behavior
Rows are inserted without error

Screenshots
If applicable, add screenshots to help explain your problem.

Environments (please complete the following information):

• OS: macOS
• go-zero version v1.10.0
• goctl version 1.9.2 darwin/arm64
• MySQL 8.0.43

More description
Add any other context about the problem here.

[kevwan]

Good catch! Confirmed — Time.String() returns a format like "2006-01-02 15:04:05.999999999 -0700 MST" which MySQL cannot parse as a DATETIME value.

The fix should use v.Format(time.DateTime) instead, which produces the "2006-01-02 15:04:05" format that MySQL expects.

Both the time.Time and *time.Time cases in writeValue need to be updated.

Thanks for the report and the fix PR in #5517!

[kevwan]

This bug has been confirmed and a fix is available in PR #5517.

Root cause: BulkInserter.writeValue() used time.Time.String() which produces Go's native format ("2006-01-02 15:04:05.999999999 -0700 MST m=+..."). MySQL rejects this format.

Fix in #5517: Uses time.Format("2006-01-02 15:04:05.999999") which produces a MySQL-compatible datetime string. Also fixes a nil-pointer bug for *time.Time values.

Workaround (until merged): Format the time value manually before passing to BulkInserter:

inserter.Insert("bob", time.Now().Format("2006-01-02 15:04:05.999999"))

Or use the MySQL driver's parseTime=true with a UTC time:

inserter.Insert("bob", time.Now().UTC())