execution: initialize next in aggregation even if we aggregate the labels away (#504)

* execution: initialize next in aggregation even if we aggregate the labels away

Signed-off-by: Michael Hoffmann <[email protected]>

* execute: review on execution/aggregate/hashaggregate.go

Co-authored-by: Filip Petkovski <[email protected]>
Signed-off-by: Michael Hoffmann <[email protected]>

---------

Signed-off-by: Michael Hoffmann <[email protected]>
Signed-off-by: Michael Hoffmann <[email protected]>
Co-authored-by: Michael Hoffmann <[email protected]>
Co-authored-by: Filip Petkovski <[email protected]>

Author: MichaHoffmann

execution/aggregate/hashaggregate.go

@@ -220,6 +220,10 @@ func (a *aggregate) initializeTables(ctx context.Context) error {
 }
 
 func (a *aggregate) initializeVectorizedTables(ctx context.Context) ([]aggregateTable, []labels.Labels, error) {
+	// perform initialization of the underlying operator even if we are aggregating the labels away
+	if _, err := a.next.Series(ctx); err != nil {
+		return nil, nil, err
+	}
 	tables, err := newVectorizedTables(a.stepsBatch, a.aggregation)
 	if errors.Is(err, parse.ErrNotSupportedExpr) {
 		return a.initializeScalarTables(ctx)