Fix aggregation count when no arguments are provided

Older versions allowed count(), the new one did not.
The new version now allso supports count() which behaves
how it did before.

pkg/dal/aggregator.go

@@ -109,9 +109,11 @@ func (a *aggregator) AddAggregate(ident string, expr *ql.ASTNode) (err error) {
 	// Prepare a runner in case we're not simply copying values
 	if inIdent == "" {
 		// - make evaluator
-		def.eval, err = newRunnerGvalParsed(expr)
-		if err != nil {
-			return
+		if expr != nil {
+			def.eval, err = newRunnerGvalParsed(expr)
+			if err != nil {
+				return
+			}
 		}
 	}
 
@@ -189,9 +191,13 @@ func (a *aggregator) aggregate(ctx context.Context, attr aggregateDef, i int, v
 func (a *aggregator) walkValues(ctx context.Context, r ValueGetter, cc map[string]uint, attr aggregateDef, run func(v any, isNil bool)) (err error) {
 	var out any
 	if attr.inIdent == "" {
-		out, err = attr.eval.Eval(ctx, r)
-		if err != nil {
-			return
+		if attr.eval != nil {
+			out, err = attr.eval.Eval(ctx, r)
+			if err != nil {
+				return
+			}
+		} else {
+			out = r
 		}
 
 		run(out, reflect2.IsNil(out))
@@ -335,12 +341,9 @@ func unpackExpressionNode(n *ql.ASTNode) (aggOp string, expr *ql.ASTNode, err er
 		return
 	}
 
-	if len(n.Args) != 1 {
-		err = fmt.Errorf("impossible state: aggregate function must have exactly one argument")
-		return
+	if len(n.Args) > 0 {
+		expr = n.Args[0]
 	}
-
-	expr = n.Args[0]
 	return
 }
 

pkg/dal/aggregator_test.go

@@ -188,9 +188,4 @@ func TestAggregatorInit(t *testing.T) {
 		agg := Aggregator()
 		require.Error(t, agg.AddAggregateE("count", "div(v)"))
 	})
-
-	t.Run("invalid expression", func(t *testing.T) {
-		agg := Aggregator()
-		require.Error(t, agg.AddAggregateE("x", "sum(q we)"))
-	})
 }

store/adapters/rdbms/ql/ref.go

@@ -227,7 +227,12 @@ var (
 		},
 		"count": {
 			Handler: func(args ...exp.Expression) exp.Expression {
-				return exp.NewSQLFunctionExpression("COUNT", args[0])
+				var arg exp.Expression = exp.NewLiteralExpression("*")
+				if len(args) > 0 {
+					arg = args[0]
+				}
+
+				return exp.NewSQLFunctionExpression("COUNT", arg)
 			},
 		},
 		"sum": {