From 1c223939446f5de0bfe2dbb3c3979925eb5c7e69 Mon Sep 17 00:00:00 2001
From: Daniel Liu <139250065@qq.com>
Date: Thu, 3 Sep 2026 17:59:55 +0800
Subject: [PATCH] fix(core): keep blocksHashCache entries unique per height
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UpdateBlocksHashCache appended unconditionally, so refreshing the
cache for a block that was already cached — which the known-block
path now does when it promotes a stored block — grew the per-height
slice with duplicate hashes. Skip the append when the hash is already
tracked; distinct fork hashes at the same height are still kept.
---
 core/blockchain.go      |  4 ++++
 core/blockchain_test.go | 16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/core/blockchain.go b/core/blockchain.go
index 54f5291c8895..134d494f437b 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io"
 	"math/big"
+	"slices"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -2309,6 +2310,9 @@ func (bc *BlockChain) UpdateBlocksHashCache(block *types.Block) []common.Hash {
 	cached, ok := bc.blocksHashCache.Get(blockNumber)
 
 	if ok {
+		if slices.Contains(cached, block.Hash()) {
+			return cached
+		}
 		hashArr := cached
 		hashArr = append(hashArr, block.Hash())
 		bc.blocksHashCache.Remove(blockNumber)
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index dc747e5e2190..d09b7e12e156 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -2495,6 +2495,22 @@ func TestBlocksHashCacheUpdate(t *testing.T) {
 			t.Error("BlocksHashCache doesn't work when inserting block solely")
 		}
 	})
+
+	t.Run("Expect repeated cache update to keep one entry per hash", func(t *testing.T) {
+		head := chain.CurrentBlock()
+		chain.UpdateBlocksHashCache(types.NewBlockWithHeader(head))
+		chain.UpdateBlocksHashCache(types.NewBlockWithHeader(head))
+		cached, _ := chain.blocksHashCache.Get(head.Number.Uint64())
+		count := 0
+		for _, hash := range cached {
+			if hash == head.Hash() {
+				count++
+			}
+		}
+		if count != 1 {
+			t.Errorf("BlocksHashCache has %d entries for head hash, want 1: %v", count, cached)
+		}
+	})
 }
 
 // TestAreTwoBlocksSamePath tests are two blocks same path.