refactor: only add pair when position seen in key

minigeth/trie/database.go

@@ -65,19 +65,27 @@ func (db *Database) insert(hash common.Hash, size int, node node) {
 	//fmt.Println("insert", hash, size)
 }
 
-// TODO: Create pairs only when seeing pos
 func genPossibleShortNodePreimage(pos int) {
 	preimages := oracle.Preimages()
 	newPreimages := make(map[common.Hash][]byte)
+
 	for _, val := range preimages {
 		node, err := decodeNode(nil, val)
 		if err != nil {
 			continue
 		}
+
 		if node, ok := node.(*shortNode); ok {
-			for i := 1; i < len(node.Key); i += 1 {
+			var begins []int
+			for i := range node.Key {
+				if node.Key[i] == byte(pos) && i+2 < len(node.Key) {
+					begins = append(begins, i+1)
+				}
+			}
+
+			for _, begin := range begins {
 				n := shortNode{
-					Key: hexToCompact(node.Key[len(node.Key)-i:]),
+					Key: hexToCompact(node.Key[begin:]),
 					Val: node.Val,
 				}
 				buf := new(bytes.Buffer)
@@ -88,7 +96,6 @@ func genPossibleShortNodePreimage(pos int) {
 				if len(preimage) < 32 {
 					continue
 				}
-
 				newPreimages[crypto.Keccak256Hash(preimage)] = preimage
 			}
 		}

minigeth/trie/trie.go

@@ -445,6 +445,9 @@ func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
 
 				// TODO: Try to cache short nodes already generated
 				genPossibleShortNodePreimage(pos)
+
+				// TODO: We might want to ignore this error and remove the panic in oracle.Preimage
+				//       in case the sister node in deletion is an extension node.
 				// remove this optimisticly? if it's not a shortNode, it doesn't do anything
 				cnode, err := t.resolve(n.Children[pos], prefix)
 				if err != nil {