for idx, column := range columns {
					if field := sch.LookUpField(column); field != nil && field.Readable {
						fields[idx] = field
						if count, ok := matchedFieldCount[column]; ok {
							// handle duplicate fields
							for _, selectField := range sch.Fields {
								if selectField.DBName == column && selectField.Readable {
									if count == 0 {
										matchedFieldCount[column]++

	fns       []func(*DB)
	callbacks []*callback
}

type callback struct {
	name      string
	before    string
	after     string
	remove    bool
	replace   bool
	match     func(*DB) bool
	handler   func(*DB)
	processor *processor
}

func (cs *callbacks) Create() *processor {
	return cs.processors["create"]
}

func (cs *callbacks) Query() *processor {
	return cs.processors["query"]
}