Assign a name to columns with binary expressions in them

The name of the column will be every measurement located inside of the
math expression in the order they are encountered in within the
expression.

Fixes #5730.

influxql/ast.go

@@ -1055,6 +1055,8 @@ func (s *SelectStatement) ColumnNames() []string {
 				continue
 			}
 			columnNames = append(columnNames, field.Name())
+		case *BinaryExpr:
+			columnNames = append(columnNames, BinaryExprName(f))
 		default:
 			// time is always first, and we already added it, so ignore it if they asked for it anywhere else.
 			if field.Name() != "time" {
@@ -2919,6 +2921,27 @@ func (e *BinaryExpr) String() string {
 	return fmt.Sprintf("%s %s %s", e.LHS.String(), e.Op.String(), e.RHS.String())
 }
 
+func BinaryExprName(expr *BinaryExpr) string {
+	v := binaryExprNameVisitor{}
+	Walk(&v, expr)
+	return strings.Join(v.names, "_")
+}
+
+type binaryExprNameVisitor struct {
+	names []string
+}
+
+func (v *binaryExprNameVisitor) Visit(n Node) Visitor {
+	switch n := n.(type) {
+	case *VarRef:
+		v.names = append(v.names, n.Val)
+	case *Call:
+		v.names = append(v.names, n.Name)
+		return nil
+	}
+	return v
+}
+
 // ParenExpr represents a parenthesized expression.
 type ParenExpr struct {
 	Expr Expr

influxql/ast_test.go

@@ -717,6 +717,29 @@ func TestSelectStatement_HasCountDistinct(t *testing.T) {
 	}
 }
 
+// Ensure binary expression names can be evaluated.
+func TestBinaryExprName(t *testing.T) {
+	for i, tt := range []struct {
+		expr string
+		name string
+	}{
+		{expr: `value + 1`, name: `value`},
+		{expr: `"user" / total`, name: `user_total`},
+		{expr: `("user" + total) / total`, name: `user_total_total`},
+	} {
+		expr := influxql.MustParseExpr(tt.expr)
+		switch expr := expr.(type) {
+		case *influxql.BinaryExpr:
+			name := influxql.BinaryExprName(expr)
+			if name != tt.name {
+				t.Errorf("%d. unexpected name %s, got %s", i, name, tt.name)
+			}
+		default:
+			t.Errorf("%d. unexpected expr type: %T", i, expr)
+		}
+	}
+}
+
 // Ensure the time range of an expression can be extracted.
 func TestTimeRange(t *testing.T) {
 	for i, tt := range []struct {