squash box changes that become no-ops

ledger/accountdb.go

@@ -3830,11 +3830,18 @@ func accountsNewRoundImpl(
 	}
 
 	updatedKVs = make(map[string]persistedKVData, len(kvPairs))
-	for key, value := range kvPairs {
-		if value.data != nil {
-			err = writer.upsertKvPair(key, value.data)
-			updatedKVs[key] = persistedKVData{value: value.data, round: lastUpdateRound}
+	for key, mv := range kvPairs {
+		if mv.data != nil {
+			// reminder: check oldData for nil here, b/c bytes.Equal conflates nil and "".
+			if mv.oldData != nil && bytes.Equal(mv.oldData, mv.data) {
+				continue // changed back within the delta span
+			}
+			err = writer.upsertKvPair(key, mv.data)
+			updatedKVs[key] = persistedKVData{value: mv.data, round: lastUpdateRound}
 		} else {
+			if mv.oldData == nil { // Came and went within the delta span
+				continue
+			}
 			err = writer.deleteKvPair(key)
 			updatedKVs[key] = persistedKVData{value: nil, round: lastUpdateRound}
 		}

ledger/acctupdates_test.go

@@ -1499,7 +1499,9 @@ func TestKVCache(t *testing.T) {
 		if i < kvCnt/kvsPerBlock {
 			for j := 0; j < kvsPerBlock; j++ {
 				name := fmt.Sprintf("%d", curKV)
-				kvMods[name] = ledgercore.KvValueDelta{Data: nil}
+				// needs an old data, else optimized away.
+				// if oldData = "" there is the best chance of a bug, so we use that
+				kvMods[name] = ledgercore.KvValueDelta{Data: nil, OldData: []byte("")}
 				curKV++
 			}
 		}

ledger/catchpointtracker.go

@@ -1015,6 +1015,7 @@ func (ct *catchpointTracker) accountsUpdateBalances(accountsDeltas compactAccoun
 			continue
 		}
 		if mv.oldData != nil {
+			// reminder: check mv.data for nil here, b/c bytes.Equal conflates nil and "".
 			if mv.data != nil && bytes.Equal(mv.oldData, mv.data) {
 				continue // changed back within the delta span
 			}