core: handle corner case in report

core/txindexer.go

@@ -250,6 +250,14 @@ func (indexer *txIndexer) loop(chain *BlockChain) {
 
 // report returns the tx indexing progress.
 func (indexer *txIndexer) report(head uint64) TxIndexProgress {
+	// Special case if the head is even below the cutoff,
+	// nothing to index.
+	if head < indexer.cutoff {
+		return TxIndexProgress{
+			Indexed:   0,
+			Remaining: 0,
+		}
+	}
 	// Compute how many blocks are supposed to be indexed
 	total := indexer.limit
 	if indexer.limit == 0 || total > head {
@@ -259,7 +267,7 @@ func (indexer *txIndexer) report(head uint64) TxIndexProgress {
 	if total > length {
 		total = length
 	}
-	// Compute how many block have been indexed
+	// Compute how many blocks have been indexed
 	var indexed uint64
 	tail := rawdb.ReadTxIndexTail(indexer.db)
 	if tail != nil {

core/txindexer_test.go

@@ -416,6 +416,15 @@ func TestTxIndexerReport(t *testing.T) {
 			expIndexed:   62,
 			expRemaining: 1,
 		},
+		{
+			// head = 128, limit = 64, cutoff = 256 => index: [66, 128]
+			head:         chainHead,
+			limit:        0,
+			cutoff:       256,
+			tail:         nil,
+			expIndexed:   0,
+			expRemaining: 0,
+		},
 	}
 	for _, c := range cases {
 		db, _ := rawdb.NewDatabaseWithFreezer(rawdb.NewMemoryDatabase(), "", "", false)