core/stateless: only report leaf depth in witness stats

core/stateless/stats.go

@@ -17,10 +17,9 @@
 package stateless
 
 import (
-	"maps"
-
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
 var (
@@ -86,17 +85,62 @@
 	}
 }
 
+// isLeafNode checks if the given RLP-encoded node data represents a leaf node.
+// In Ethereum's Modified Merkle Patricia Trie, a leaf node is identified by:
+// - Having exactly 2 RLP list elements (for both shortNode and leafNode encodings)
+// - The second element being a value (not a hash reference to another node)
+func isLeafNode(nodeData []byte) bool {
+	if len(nodeData) == 0 {
+		return false
+	}
+
+	// Decode the RLP list
+	var elems [][]byte
+	if err := rlp.DecodeBytes(nodeData, &elems); err != nil {
+		return false
+	}
+
+	// A leaf node in MPT has exactly 2 elements: [key, value]
+	// An extension node also has 2 elements but the value is a hash (32 bytes)
+	if len(elems) != 2 {
+		return false // Branch nodes have 17 elements
+	}
+
+	// If the second element is 32 bytes, it's likely a hash reference (extension node)
+	// Leaf nodes typically have values that are not exactly 32 bytes
+	// However, this is not a perfect heuristic as values could be 32 bytes
+	// A more accurate check would require checking the key's terminator flag
+
+	// Check if the key has a terminator (indicates leaf node)
+	// In compact encoding, the first nibble of the key indicates the node type
+	if len(elems[0]) > 0 {
+		// Get the first byte which contains the flags
+		flags := elems[0][0]
+		// Check if the terminator flag is set (bit 5)
+		// Leaf nodes have the terminator flag set (0x20 or 0x30)
+		return (flags & 0x20) != 0
+	}
+
+	return false
+}
+
 // Add records trie access depths from the given node paths.
 // If `owner` is the zero hash, accesses are attributed to the account trie;
 // otherwise, they are attributed to the storage trie of that account.
 func (s *WitnessStats) Add(nodes map[string][]byte, owner common.Hash) {
 	if owner == (common.Hash{}) {
-		for path := range maps.Keys(nodes) {
-			s.accountTrie.add(int64(len(path)))
+		for path, nodeData := range nodes {
+			// Only record depth for leaf nodes
+			if isLeafNode(nodeData) {
+				s.accountTrie.add(int64(len(path)))
+			}
 		}
 	} else {
-		for path := range maps.Keys(nodes) {
-			s.storageTrie.add(int64(len(path)))
+		for path, nodeData := range nodes {
+			// Only record depth for leaf nodes
+			if isLeafNode(nodeData) {
+				s.storageTrie.add(int64(len(path)))
+			}
 		}
 	}
 }

core/stateless/stats_test.go

@@ -0,0 +1,176 @@
+// Copyright 2025 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package stateless
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+func TestIsLeafNode(t *testing.T) {
+	tests := []struct {
+		name     string
+		nodeData []byte
+		want     bool
+	}{
+		{
+			name: "leaf node with terminator",
+			// Compact encoding: first byte 0x20 means odd length key with terminator
+			// This represents a leaf node
+			nodeData: mustEncodeNode(t, [][]byte{
+				{0x20, 0x01, 0x02, 0x03}, // Key with terminator flag
+				{0x01, 0x02, 0x03, 0x04},  // Value
+			}),
+			want: true,
+		},
+		{
+			name: "leaf node with even key and terminator",
+			// Compact encoding: first byte 0x30 means even length key with terminator
+			nodeData: mustEncodeNode(t, [][]byte{
+				{0x30, 0x01, 0x02}, // Key with terminator flag (even length)
+				{0x05, 0x06},        // Value
+			}),
+			want: true,
+		},
+		{
+			name: "extension node (no terminator)",
+			// Compact encoding: first byte 0x00 means even length key without terminator
+			// This represents an extension node
+			nodeData: mustEncodeNode(t, [][]byte{
+				{0x00, 0x01, 0x02},                                                              // Key without terminator flag
+				{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, // 32-byte hash
+					0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a,
+					0x1b, 0x1c, 0x1d, 0x1e, 0x1f},
+			}),
+			want: false,
+		},
+		{
+			name: "extension node with odd key (no terminator)",
+			// Compact encoding: first byte 0x10 means odd length key without terminator
+			nodeData: mustEncodeNode(t, [][]byte{
+				{0x10, 0x01, 0x02, 0x03}, // Key without terminator flag (odd length)
+				{0x01, 0x02, 0x03, 0x04}, // Could be hash reference
+			}),
+			want: false,
+		},
+		{
+			name: "branch node",
+			// Branch nodes have 17 elements
+			nodeData: mustEncodeNode(t, [][]byte{
+				{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {},
+			}),
+			want: false,
+		},
+		{
+			name:     "empty data",
+			nodeData: []byte{},
+			want:     false,
+		},
+		{
+			name:     "invalid RLP",
+			nodeData: []byte{0xff, 0xff, 0xff},
+			want:     false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isLeafNode(tt.nodeData)
+			if got != tt.want {
+				t.Errorf("isLeafNode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func mustEncodeNode(t *testing.T, elems [][]byte) []byte {
+	data, err := rlp.EncodeToBytes(elems)
+	if err != nil {
+		t.Fatalf("Failed to encode node: %v", err)
+	}
+	return data
+}
+
+func TestWitnessStats(t *testing.T) {
+	// Create a witness stats collector
+	stats := NewWitnessStats()
+
+	// Create witness data with both leaf and non-leaf nodes
+	witness := map[string][]byte{
+		// Leaf node at depth 4 (path length 4)
+		"abcd": mustEncodeNode(t, [][]byte{
+			{0x20, 0x01, 0x02}, // Key with terminator
+			{0x01, 0x02},        // Value
+		}),
+		// Extension node at depth 2 (should not be counted)
+		"ab": mustEncodeNode(t, [][]byte{
+			{0x00, 0x01, 0x02}, // Key without terminator
+			{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d,
+				0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a,
+				0x1b, 0x1c, 0x1d, 0x1e, 0x1f}, // 31-byte hash (simulated)
+		}),
+		// Another leaf node at depth 6
+		"abcdef": mustEncodeNode(t, [][]byte{
+			{0x30, 0x01}, // Key with terminator
+			{0x03, 0x04}, // Value
+		}),
+		// Branch node (should not be counted)
+		"a": mustEncodeNode(t, [][]byte{
+			{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {},
+		}),
+	}
+
+	// Add account trie data (zero owner hash)
+	stats.Add(witness, common.Hash{})
+
+	// Verify only leaf nodes were counted
+	if stats.accountTrie.samples != 2 {
+		t.Errorf("Expected 2 leaf nodes in account trie, got %d", stats.accountTrie.samples)
+	}
+
+	// Check the depth statistics
+	expectedAvg := int64((4 + 6) / 2) // Average of path lengths 4 and 6
+	if stats.accountTrie.totalDepth/stats.accountTrie.samples != expectedAvg {
+		t.Errorf("Expected average depth %d, got %d", expectedAvg, stats.accountTrie.totalDepth/stats.accountTrie.samples)
+	}
+	if stats.accountTrie.minDepth != 4 {
+		t.Errorf("Expected min depth 4, got %d", stats.accountTrie.minDepth)
+	}
+	if stats.accountTrie.maxDepth != 6 {
+		t.Errorf("Expected max depth 6, got %d", stats.accountTrie.maxDepth)
+	}
+
+	// Test storage trie (non-zero owner hash)
+	storageStats := NewWitnessStats()
+	storageWitness := map[string][]byte{
+		// Leaf node
+		"xyz": mustEncodeNode(t, [][]byte{
+			{0x20, 0x01}, // Key with terminator
+			{0x05, 0x06}, // Value
+		}),
+	}
+	storageStats.Add(storageWitness, common.HexToHash("0x1234"))
+
+	if storageStats.storageTrie.samples != 1 {
+		t.Errorf("Expected 1 leaf node in storage trie, got %d", storageStats.storageTrie.samples)
+	}
+	if storageStats.accountTrie.samples != 0 {
+		t.Errorf("Expected 0 nodes in account trie for storage access, got %d", storageStats.accountTrie.samples)
+	}
+}