transactions: Simplify computation of voter state

In order to determine the voter state in a transaction, we iterate
through all subtransactions and soak up the result in there. But given
that subtransactions are always created with all voters of the
transaction, we know that on each iteration, we'll override all results
of the preceding subtransaction anyway. Ultimately, we thus end up with
the state as recorded by the last subtransaction, and it's clear that
the iteration is pointless.

Simplify the code to just take the state of the last subtransaction.

1 files changed, 6 insertions, 6 deletions

diff --git a/internal/praefect/transactions/transaction.go b/internal/praefect/transactions/transaction.go
index 2476c0b31..784531404 100644
--- a/internal/praefect/transactions/transaction.go
+++ b/internal/praefect/transactions/transaction.go
@@ -166,12 +166,12 @@ func (t *transaction) State() (map[string]VoteResult, error) {
 		return results, nil
 	}
 
-	// Collect all subtransactions. As they are ordered by reverse recency, we can simply
-	// overwrite our own results.
-	for _, subtransaction := range t.subtransactions {
-		for voter, result := range subtransaction.state() {
-			results[voter] = result
-		}
+	// Collect voter results. Given that all subtransactions are created with all voters
+	// registered in the transaction, we can simply take results from the last subtransaction.
+	// Any nodes which didn't yet cast a vote in the last transaction will be in the default
+	// undecided state.
+	for voter, result := range t.subtransactions[len(t.subtransactions)-1].state() {
+		results[voter] = result
 	}
 
 	return results, nil