Create ROW helper for adhoc decoding of records

composite_test.go

@@ -71,7 +71,20 @@ create type mytype as (
 	}
 
 	fmt.Printf("Second row: %v\n", result)
+
+	// Adhoc rows can be decoded inplace without boilerplate (works with composite types too)
+	var isNull bool
+	var a int
+	var b *string
+
+	if err = conn.QueryRow(context.Background(), "select (2, 'bar')::mytype", pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(pgtype.ROW(&isNull, &a, &b)); err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("Adhoc: isNull=%v a=%d b=%s", isNull, a, *b)
+
 	// Output:
 	// First row: a=1 b=foo
 	// Second row: <nil>
+	// Adhoc: isNull=false a=2 b=bar
 }

convert.go

@@ -471,6 +471,34 @@ func ScanRowValue(ci *ConnInfo, src []byte, dst ...Value) error {
 	return nil
 }
 
+// ROW allows deconstructing row values (records and composite types) into
+// fields directly without creating your own type and implementing decoder interfaces
+func ROW(isNull *bool, fields ...interface{}) BinaryDecoderFunc {
+	return func(ci *ConnInfo, src []byte) error {
+		var record Record
+		if err := record.DecodeBinary(ci, src); err != nil {
+			return err
+		}
+
+		if record.Status == Null {
+			*isNull = true
+			return nil
+		}
+
+		if len(record.Fields) != len(fields) {
+			return errors.Errorf("can't scan row value, number of fields don't match: row fields count=%d desired fields count=%d", len(record.Fields), len(fields))
+		}
+
+		for i, f := range record.Fields {
+			if err := f.AssignTo(fields[i]); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+}
+
 func init() {
 	kindTypes = map[reflect.Kind]reflect.Type{
 		reflect.Bool:    reflect.TypeOf(false),

pgtype.go

@@ -158,6 +158,15 @@ type TextEncoder interface {
 	EncodeText(ci *ConnInfo, buf []byte) (newBuf []byte, err error)
 }
 
+//The BinaryDecoderFunc type is an adapter to allow the use of ordinary functions as BinaryDecoder types.
+// If f is a function with the appropriate signature, BinaryDecoderFunc(f) is a BinaryDecoder that calls f.
+type BinaryDecoderFunc func(ci *ConnInfo, src []byte) error
+
+// DecodeBinary calls f(ci, src)
+func (f BinaryDecoderFunc) DecodeBinary(ci *ConnInfo, src []byte) error {
+	return f(ci, src)
+}
+
 var errUndefined = errors.New("cannot encode status undefined")
 var errBadStatus = errors.New("invalid status")