You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: region.xo.go
    path of file: ./repos/xo/_examples/northwind/mysql
    
    the code of the file until where you have to start completion: package mysql

// Code generated by xo. DO NOT EDIT.

import (
	"context"
)

// Region represents a row from 'northwind.region'.
type Region struct {
	RegionID          int16  `json:"region_id"`          // region_id
	RegionDescription string `json:"region_description"` // region_description
	// xo fields
	_exists, _deleted bool
}

// Exists returns true when the [Region] exists in the database.
func (r *Region) E
    
func (r *Region) Upsert(ctx context.Context, db DB) error {
	switch {
	case r._deleted: // deleted
		return logerror(&ErrUpsertFailed{ErrMarkedForDeletion})
	}
	// upsert
	const sqlstr = `INSERT INTO northwind.region (` +
		`region_id, region_description` +
		`) VALUES (` +
		`?, ?` +
		`)` +
		` ON DUPLICATE KEY UPDATE ` +
		`region_id = VALUES(region_id), region_description = VALUES(region_description)`
	// run
	logf(sqlstr, r.RegionID, r.RegionDescription)
	if _, err := db.ExecContext(ctx, sqlstr, r.RegionID, r.RegionDescription); err != nil {
		return logerror(err)
	}
	// set exists
	r._exists = true
	return nil
}