From 1100dba9650d333a0b17ed3b17a60d7fe3bb03f0 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Tue, 18 Mar 2025 21:08:16 +0100
Subject: [PATCH] core/rawdb: improve PruneTransactionIndex

---
 core/rawdb/chain_iterator.go      | 16 +++++++++++++---
 core/rawdb/chain_iterator_test.go |  3 +++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/core/rawdb/chain_iterator.go b/core/rawdb/chain_iterator.go
index 9c62a63b66..64d252f31b 100644
--- a/core/rawdb/chain_iterator.go
+++ b/core/rawdb/chain_iterator.go
@@ -366,10 +366,19 @@ func unindexTransactionsForTesting(db ethdb.Database, from uint64, to uint64, in
 
 // PruneTransactionIndex removes all tx index entries below a certain block number.
 func PruneTransactionIndex(db ethdb.Database, pruneBlock uint64) {
-	db = NewTable(db, string(txLookupPrefix))
-	iter := db.NewIterator(nil, nil)
-	defer iter.Release()
+	tail := ReadTxIndexTail(db)
+	if tail == nil {
+		return // no index
+	}
+	if *tail > pruneBlock {
+		return // index ends above pruneBlock
+	}
 
+	// There are transactions below pruneBlock in the index. Iterate the entire index to
+	// remove the entries. Note if this fails, the index is messed up, but tail still
+	// points to the old tail.
+	iter := db.NewIterator(txLookupPrefix, nil)
+	defer iter.Release()
 	for iter.Next() {
 		v := iter.Value()
 		if len(v) > 8 {
@@ -383,6 +392,7 @@ func PruneTransactionIndex(db ethdb.Database, pruneBlock uint64) {
 			}
 		}
 	}
+	WriteTxIndexTail(db, pruneBlock)
 }
 
 func decodeNumber(b []byte) uint64 {
diff --git a/core/rawdb/chain_iterator_test.go b/core/rawdb/chain_iterator_test.go
index cb6119baaa..b6cc5388a4 100644
--- a/core/rawdb/chain_iterator_test.go
+++ b/core/rawdb/chain_iterator_test.go
@@ -245,6 +245,9 @@ func TestPruneTransactionIndex(t *testing.T) {
 			if block.NumberU64() < pruneBlock && num != nil {
 				t.Fatalf("TxLookup entry not removed: %x -> %v", tx.Hash(), num)
 			}
+			if block.NumberU64() > pruneBlock && (num == nil || *num != block.NumberU64()) {
+				t.Fatalf("wrong TxLookup entry after pruning: %x -> %v", tx.Hash(), num)
+			}
 		}
 	}
 }