Iterative Optimization on Hot Paths: Optimization 2: Cutting out the middleman

sqlgen.go.diff

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
+	}

	if err := rows.Scan(values...); err != nil {
		return nil, err
	}
-	for i, column := range table.Columns {
-		scanners[i].CopyTo(elem.FieldByIndex(column.Index))
-	}

	return ptr.Interface(), nil
}