KIP-111 Use ExtHash in trie database

[blukat29]

Proposed changes

Use ExtHash type throught the trie-handling code. This is a step towards implmementing the KIP-111 State Pruning. This PR must not change any behavior of the Klaytn node.

Methodology

Identify trie node hashes in the codebase. Convert the variable type, function argument type, and return types (collectively "hash types") to ExtHash if needed. Trie node hashes can be categorized into three.

1. State root - Root of a world state trie associated to a block, i.e. block.Root().
2. Storage root - Root of a contract storage trie dedicated to each contract account, i.e. account.StorageRoot().
3. Child node - Child nodes in the both tries.

If a value always conveys State roots, then keep the hash type common.Hash.
If a value can potentially carry Storage roots or Child nodes, then make the hash type to common.ExtHash.

For example StateDB.IntermediateRoot() common.Hash kept its type because it is the State root.
In contrast, DBManager.ReadTrieNode(common.ExtHash) changed its type because it receives all kinds of node hashes.

CodeHash (contract bytecode) is unrelated to trie nodes, so it stays common.Hash.

Use hash.ExtendLegacy() and exthash.Unextend() to convert between the two types.
After this PR, any ExtHash value flowing in the codebase must be extended with Legacy Nonce.

Notable changes

• DiskDB - DBManager: All TrieNode accessors uses ExtHash. Code accessors are Hash.
  Trie node keyed by ExtHashLegacy (i.e. hash.ExtendLegacy()) are stored with 32-byte key (i.e. db.Put(exthash.Unextend(), node))

  • Modified interfaces ProofDBReader and StateTrieReadDB accordingly.
  • Removed struct stateTrieMigrationDB in favor of DBManager.

• Node encoding: Trie nodes may contain ExtHash references to other trie nodes. Encoding and Decoding mechanisms are updated.

  • decodeNode() can decode both Hash and ExtHash references.
  • hasher.hashRoot() injects either Hash or ExtHash when encoding the nodes.
  • See node_test.go and hasher_test.go for details.

• TrieDB - Database: Most internal fields and methods carry ExtHash. Below are the exceptional cases.

  • Reference(H,H) is diversified into
    • Reference(EH,EH) for linking state trie leaf (EH) and storage trie root (EH)
    • ReferenceRoot(H) for referencing the State root (H)
  • Dereference(H) is left untouched because it's exclusively used with State root (H)
  • Commit(H) is left untouched because it's exclusively used with State root (H)

• TrieDB - Trie: trie node references are internally stored in hashNode == []byte, so not much type changes.
  However, some functions are diversified into two variants.

  • NewTrie(H) and NewSecureTrie(H) open State tries. They are left untouched because it's only for State root.
  • NewStorageTrie(EH) and NewSecureStorageTrie(EH) open account storage tries. They accept ExtHash as root hash.
  • Hash() and Commit() returns the

• Contract Account: A contract account (CA), contains a reference to its Storage root. Therefore its encoding format must change.

  • The field SmartContractAccount.StorageRoot is now ExtHash.
  • Methods GetStorageRoot() and SetStorageRoot handles ExtHash.
  • Contracts accounts are RLP-encoded before stored in database. In its encoding, the Storage root may be represented in Hash or ExtHash.
    • AccountSerializer can decode both formats.
    • AccountSerializer can choose to encode into one of the two formats.

Full list of changes are available in the table in Further Comments section.

Types of changes

• Bugfix
• New feature or enhancement
• Others

Checklist

• I have read the CONTRIBUTING GUIDELINES doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes ($ make test)
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

Further comments

Comprehensive list of hash type changes. = means interface unchanged, ~ means changed, + means newly added.

Scope	Before	After	Commits
DiskDB	TrieNodeKey (H) ReadTrieNode (H) HasTrieNode (H) WriteTrieNode (H) PutTrieNodeToBatch (H) DeleteTrieNode (H) interface ProofDBReader {H} interface StateTrieReadDB {H}	~ TrieNodeKey (EH) ~ ReadTrieNode (EH) ~ HasTrieNode (EH) ~ WriteTrieNode (EH) ~ PutTrieNodeToBatch (EH) ~ DeleteTrieNode (EH) ~ interface ProofDBReader {EH} ~ interface StateTrieReadDB {EH}	9b6cfa9
node encoding	decodeNode (H) hasher.hash ()->H	~ decodeNode (EH) ~ hasher.hash ()->EH	603e9b8 61b175b
TrieDB	node (H) Node (H) NodeFromOld (H) DoesExistCachedNode (H) DoesExistNodeInPersistent (H) Nodes ()->[]H NodeChildren (H)->[]H CollectChildrenStats (H) insert (H) Reference (H,H) - Dereference (H) Commit (H)	~ node (EH) ~ Node (EH) ~ NodeFromOld (EH) ~ DoesExistCachedNode (EH) ~ DoesExistNodeInPersistent (EH) ~ Nodes ()->[]EH ~ NodeChildren (EH)->[]EH ~ CollectChildrenStats (EH) ~ insert (EH) ~ Reference (EH,EH) + ReferenceRoot (H) = Dereference (H) = Commit(H)	15f0b58 29d069f 2968339
Trie	NewTrie (H) - NewSecureTrie (H) - OpenTrie (H) OpenStorageTrie (H) Hash ()->H - Commit ()->H - LeafCallback (H)	= NewTrie (H) + NewStorageTrie (EH) = NewSecureTrie (H) + NewSecureStorageTrie (EH) = OpenTrie (H) + OpenStorageTrie (EH) = Hash ()->H + HashExt ()->EH = Commit ()->H + CommitExt ()->EH ~ LeafCallback (EH)	bc40be2
Proof	VerifyProof (H) VerifyRangeProof (H)	= VerifyProof (H) = VerifyRangeProof (H)
TrieSync	request {H} SyncResult {H} AddSubTrie (H) AddCodeEntry (parent H) Missing ()->(nodes []H)	= request {H} = SyncResult {H} = AddSubTrie (H) = AddCodeEntry (parent H) = Missing ()->(nodes []H)
Iterator	statedb.nodeIterator.Hash ()->H statedb.nodeIterator.Parent ()->H state.NodeIterator.Hash: H state.NodeIterator.Parent: H	= statedb.nodeIterator.Hash ()->H = statedb.nodeIterator.Parent ()->H = state.NodeIterator.Hash: H = state.NodeIterator.Parent: H
StateDB	IntermediateRoot ()->H Commit ()->H Reset (H) GetContractStorageRoot ()->H openStorageTrie (H)	= IntermediateRoot ()->H = Commit ()->H = Reset (H) ~ GetContractStorageRoot ()->EH ~ openStorageTrie (EH)	e62143f 3e408ff
Contract Account	SmartContractAccount {H} GetStorageRoot ()->H SetStorageRoot (H)	~ SmartContractAccount {EH} ~ GetStorageRoot ()->EH ~ SetStorageRoot (EH)	eff7caf 860507d