Allow reading a result row multiple times

refs #478

query_test.go

@@ -161,6 +161,51 @@ func TestConnQueryValues(t *testing.T) {
 	}
 }
 
+// https://github.com/jackc/pgx/issues/478
+func TestConnQueryReadRowMultipleTimes(t *testing.T) {
+	t.Parallel()
+
+	conn := mustConnectString(t, os.Getenv("PGX_TEST_DATABASE"))
+	defer closeConn(t, conn)
+
+	var rowCount int32
+
+	rows, err := conn.Query(context.Background(), "select 'foo'::text, 'bar'::varchar, n, null, n from generate_series(1,$1) n", 10)
+	require.NoError(t, err)
+	defer rows.Close()
+
+	for rows.Next() {
+		rowCount++
+
+		for i := 0; i < 2; i++ {
+			values, err := rows.Values()
+			require.NoError(t, err)
+			require.Len(t, values, 5)
+			require.Equal(t, "foo", values[0])
+			require.Equal(t, "bar", values[1])
+			require.Equal(t, rowCount, values[2])
+			require.Nil(t, values[3])
+			require.Equal(t, rowCount, values[4])
+
+			var a, b string
+			var c int32
+			var d pgtype.Unknown
+			var e int32
+
+			err = rows.Scan(&a, &b, &c, &d, &e)
+			require.NoError(t, err)
+			require.Equal(t, "foo", a)
+			require.Equal(t, "bar", b)
+			require.Equal(t, rowCount, c)
+			require.Equal(t, pgtype.Null, d.Status)
+			require.Equal(t, rowCount, e)
+		}
+	}
+
+	require.NoError(t, rows.Err())
+	require.Equal(t, int32(10), rowCount)
+}
+
 // https://github.com/jackc/pgx/issues/386
 func TestConnQueryValuesWithMultipleComplexColumnsOfSameType(t *testing.T) {
 	t.Parallel()

rows.go

@@ -81,7 +81,6 @@ type connRows struct {
 	connInfo  *pgtype.ConnInfo
 	values    [][]byte
 	rowCount  int
-	columnIdx int
 	err       error
 	startTime time.Time
 	sql       string
@@ -151,7 +150,6 @@ func (rows *connRows) Next() bool {
 
 	if rows.resultReader.NextRow() {
 		rows.rowCount++
-		rows.columnIdx = 0
 		rows.values = rows.resultReader.Values()
 		return true
 	} else {
@@ -160,21 +158,6 @@ func (rows *connRows) Next() bool {
 	}
 }
 
-func (rows *connRows) nextColumn() ([]byte, *pgproto3.FieldDescription, bool) {
-	if rows.closed {
-		return nil, nil, false
-	}
-	if len(rows.FieldDescriptions()) <= rows.columnIdx {
-		rows.fatal(errors.New("No next column available"))
-		return nil, nil, false
-	}
-
-	buf := rows.values[rows.columnIdx]
-	fd := &rows.FieldDescriptions()[rows.columnIdx]
-	rows.columnIdx++
-	return buf, fd, true
-}
-
 func (rows *connRows) Scan(dest ...interface{}) error {
 	if len(rows.FieldDescriptions()) != len(dest) {
 		err := errors.Errorf("Scan received wrong number of arguments, got %d but expected %d", len(dest), len(rows.FieldDescriptions()))
@@ -183,7 +166,8 @@ func (rows *connRows) Scan(dest ...interface{}) error {
 	}
 
 	for i, d := range dest {
-		buf, fd, _ := rows.nextColumn()
+		buf := rows.values[i]
+		fd := &rows.FieldDescriptions()[i]
 
 		if d == nil {
 			continue
@@ -206,8 +190,9 @@ func (rows *connRows) Values() ([]interface{}, error) {
 
 	values := make([]interface{}, 0, len(rows.FieldDescriptions()))
 
-	for range rows.FieldDescriptions() {
-		buf, fd, _ := rows.nextColumn()
+	for i := range rows.FieldDescriptions() {
+		buf := rows.values[i]
+		fd := &rows.FieldDescriptions()[i]
 
 		if buf == nil {
 			values = append(values, nil)