Fix aggregator incorrectly determining if we're copying values

In case the expression uses simple attr. reference, there is no
need to initialize expr. runners.
The old logic didn't do this correctly.

pkg/dal/aggregator.go

@@ -98,7 +98,6 @@ func (a *aggregator) AddAggregate(ident string, expr *ql.ASTNode) (err error) {
 	// Take it from the source
 	if inIdent != "" {
 		def.inIdent = inIdent
-		return
 	}
 
 	// Take it from the expression
@@ -107,16 +106,18 @@ func (a *aggregator) AddAggregate(ident string, expr *ql.ASTNode) (err error) {
 	if err != nil {
 		return
 	}
-	// - make evaluator
-	def.eval, err = newRunnerGvalParsed(expr)
-	if err != nil {
-		return
+	// Prepare a runner in case we're not simply copying values
+	if inIdent == "" {
+		// - make evaluator
+		def.eval, err = newRunnerGvalParsed(expr)
+		if err != nil {
+			return
+		}
 	}
 
 	a.aggregates = append(a.aggregates, 0)
 	a.counts = append(a.counts, 0)
 	a.def = append(a.def, def)
-
 	return
 }
 
@@ -316,8 +317,9 @@ func (a *aggregator) completeAverage() {
 // Utilities
 
 func unpackMappingSource(n *ql.ASTNode) (ident string, expr *ql.ASTNode, err error) {
-	if n.Symbol != "" {
-		return n.Symbol, nil, nil
+	// Check if first arg of agg. fnc. is an attr.
+	if len(n.Args) == 1 && n.Args[0].Symbol != "" {
+		return n.Args[0].Symbol, n, nil
 	}
 
 	expr = n
@@ -325,7 +327,6 @@ func unpackMappingSource(n *ql.ASTNode) (ident string, expr *ql.ASTNode, err err
 }
 
 func unpackExpressionNode(n *ql.ASTNode) (aggOp string, expr *ql.ASTNode, err error) {
-	// @todo check for supported aggregators
 	if n.Ref != "" {
 		aggOp = strings.ToLower(n.Ref)
 	}