berfarah

func makeWhere(table *Table, filter Filter) (*SimpleWhere, error) {
	for name, value := range filter {
		// ...
-		l = append(l, whereElem{column: column, value: column.Descriptor.Valuer(reflect.ValueOf(value))})
+		v, err := column.Descriptor.Valuer(reflect.ValueOf(value)).Value()
+		if err != nil {
+			return nil, err
+		}
+		l = append(l, whereElem{column: column, value: v})
	}

berfarah

func parseQueryRow(table *Table, rows *sql.Rows) (interface{}, error) {
	// ...
-	values := make([]interface{}, len(table.Columns))
+	values := table.Scanners.Get().([]interface{})
+	defer table.Scanners.Put(values)

	for i, column := range table.Columns {
-		scanner := column.Descriptor.Scanner()
-		scanner.Target(field)
-		values[i] = scanner

berfarah

func parseQueryRow(table *Table, rows *sql.Rows) (interface{}, error) {
	ptr := reflect.New(table.Type)
	elem := ptr.Elem()

	values := make([]interface{}, len(table.Columns))
-	[... populate scanners slice with column.Descriptor.Scanner() ...]
+	for i, column := range table.Columns {
+		scanner := column.Descriptor.Scanner()
+		scanner.Target(field)
+		values[i] = scanner

berfarah

// goodbye reflect.New in Scanner.Scan
func (s *Scanner) Scan(src interface{}) error {
-	s.value = reflect.New(s.Type)
+	// Clear out the value after a scan so we aren't holding onto references.
+	defer func() { s.value = reflect.Value{} }()
	// ...
}

// and hello Scanner.Target
+func (s *Scanner) Target(value reflect.Value) {

berfarah

// Valuer creates a sql/driver.Valuer from the type and value.
-func (d Descriptor) Valuer(val reflect.Value) Valuer {
+func (d *Descriptor) Valuer(val reflect.Value) Valuer {
-	return Valuer{Descriptor: &d, value: val}
+	return Valuer{Descriptor: d, value: val}
 }

// Scanner creates a sql.Scanner from the descriptor.
-func (d Descriptor) Scanner() *Scanner { return &Scanner{Descriptor: &d} }
+func (d *Descriptor) Scanner() *Scanner { return &Scanner{Descriptor: d} }

berfarah

type Descriptor struct {
	Tags TagSet       // struct tags
	Type reflect.Type // the original type
	Kind reflect.Kind // the underlying kind
	Ptr  bool         // whether or not it's a ptr
}

berfarah

type Scanner interface {
	// the docs tell us that the src will be a valid driver.Value
	Scan(src interface{}) error
}

berfarah

type Valuer interface {
	Value() (driver.Value, error)
}

berfarah

id := 5
var name string
err := db.QueryRowContext(ctx, "SELECT name FROM users WHERE id = ?", id).Scan(&name)

berfarah

type User struct {
	ID            int64 `sql:",primary"`
	Name          string
	Configuration Configuration `sql:",json"`
}