From 1b5a867eec711d83abfda18f7083f0c64a50f8b2 Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Sat, 22 Aug 2020 18:12:04 +0200
Subject: [PATCH] core: do less lookups when writing fast-sync block bodies
 (#21468)

---
 core/blockchain.go | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/core/blockchain.go b/core/blockchain.go
index 8434d2193f..948242ed89 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1277,6 +1277,7 @@ func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain [
 	}
 	// writeLive writes blockchain and corresponding receipt chain into active store.
 	writeLive := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
+		skipPresenceCheck := false
 		batch := bc.db.NewBatch()
 		for i, block := range blockChain {
 			// Short circuit insertion if shutting down or processing failed
@@ -1287,9 +1288,17 @@ func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain [
 			if !bc.HasHeader(block.Hash(), block.NumberU64()) {
 				return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
 			}
-			if bc.HasBlock(block.Hash(), block.NumberU64()) {
-				stats.ignored++
-				continue
+			if !skipPresenceCheck {
+				// Ignore if the entire data is already known
+				if bc.HasBlock(block.Hash(), block.NumberU64()) {
+					stats.ignored++
+					continue
+				} else {
+					// If block N is not present, neither are the later blocks.
+					// This should be true, but if we are mistaken, the shortcut
+					// here will only cause overwriting of some existing data
+					skipPresenceCheck = true
+				}
 			}
 			// Write all the data out into the database
 			rawdb.WriteBody(batch, block.Hash(), block.NumberU64(), block.Body())