change signature of MultiBufferProductPlan

Author: uchijo

plan/multi_buffer_product_plan.go

@@ -89,12 +89,26 @@ func (m *MultiBufferProductPlan) copyRecordsFrom(p Plan) (*query.TempTable, erro
 	return tt, nil
 }
 
-func (m *MultiBufferProductPlan) BlocksAccessed() int {
+func (m *MultiBufferProductPlan) BlocksAccessed() (int, error) {
 	// this guesses at the # of chunks
 	availabble := m.tx.AvailableBuffs()
-	size := NewMaterializePlan(m.tx, m.rhs).BlocksAccessed()
+	size, err := NewMaterializePlan(m.tx, m.rhs).BlocksAccessed()
+	if err != nil {
+		return 0, fmt.Errorf("failed to calculate MaterializedPlan's block access in MultiBufferProductPlan#BlockAccess: %w", err)
+	}
 	numChunks := size / int(availabble)
-	return m.rhs.BlocksAccessed() + (m.lhs.BlocksAccessed() * numChunks)
+
+	rhsBlockAccesses, err := m.rhs.BlocksAccessed()
+	if err != nil {
+		return 0, fmt.Errorf("failed to calculate rhs block access in MultiBufferProductPlan#BlockAccess: %w", err)
+	}
+
+	lhsBlockAccesses, err := m.lhs.BlocksAccessed()
+	if err != nil {
+		return 0, fmt.Errorf("failed to calculate lhs block access in MultiBufferProductPlan#BlockAccess: %w", err)
+	}
+
+	return rhsBlockAccesses + (lhsBlockAccesses * numChunks), nil
 }
 
 func (m *MultiBufferProductPlan) DistinctValues(fldName string) int {