Make benchmark tests pass

A new query object is needed for each evaulation,
as the iterators would otherwise be shared across evaluations.

promql/test.go

@@ -141,15 +141,15 @@ func (t *Test) parseEval(lines []string, i int) (int, *evalCmd, error) {
 	}
 	parts := patEvalInstant.FindStringSubmatch(lines[i])
 	var (
-		mod = parts[1]
-		at  = parts[2]
-		qry = parts[3]
+		mod  = parts[1]
+		at   = parts[2]
+		expr = parts[3]
 	)
-	expr, err := ParseExpr(qry)
+	_, err := ParseExpr(expr)
 	if err != nil {
 		if perr, ok := err.(*ParseErr); ok {
 			perr.Line = i + 1
-			perr.Pos += strings.Index(lines[i], qry)
+			perr.Pos += strings.Index(lines[i], expr)
 		}
 		return i, nil, err
 	}
@@ -301,7 +301,7 @@ func (cmd *loadCmd) append(a storage.Appender) error {
 // evalCmd is a command that evaluates an expression for the given time (range)
 // and expects a specific result.
 type evalCmd struct {
-	expr       Expr
+	expr       string
 	start, end time.Time
 	interval   time.Duration
 
@@ -321,7 +321,7 @@ func (e entry) String() string {
 	return fmt.Sprintf("%d: %s", e.pos, e.vals)
 }
 
-func newEvalCmd(expr Expr, start, end time.Time, interval time.Duration) *evalCmd {
+func newEvalCmd(expr string, start, end time.Time, interval time.Duration) *evalCmd {
 	return &evalCmd{
 		expr:     expr,
 		start:    start,
@@ -465,7 +465,8 @@ func (t *Test) exec(tc testCommand) error {
 		}
 
 	case *evalCmd:
-		q := t.queryEngine.newQuery(t.storage, cmd.expr, cmd.start, cmd.end, cmd.interval)
+		qry, _ := ParseExpr(cmd.expr)
+		q := t.queryEngine.newQuery(t.storage, qry, cmd.start, cmd.end, cmd.interval)
 		res := q.Exec(t.context)
 		if res.Err != nil {
 			if cmd.fail {