diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 47f20a56f..e141241c1 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -1,1130 +1,1150 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Copyright (c) 2017-2020 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <wallet/walletdb.h>
 
 #include <chainparams.h>
 #include <fs.h>
 #include <key_io.h>
 #include <protocol.h>
 #include <serialize.h>
 #include <sync.h>
 #include <util/bip32.h>
 #include <util/system.h>
 #include <util/time.h>
 #include <wallet/wallet.h>
 
 #include <atomic>
 
 namespace DBKeys {
 const std::string ACENTRY{"acentry"};
 const std::string ACTIVEEXTERNALSPK{"activeexternalspk"};
 const std::string ACTIVEINTERNALSPK{"activeinternalspk"};
 const std::string BESTBLOCK_NOMERKLE{"bestblock_nomerkle"};
 const std::string BESTBLOCK{"bestblock"};
 const std::string CRYPTED_KEY{"ckey"};
 const std::string CSCRIPT{"cscript"};
 const std::string DEFAULTKEY{"defaultkey"};
 const std::string DESTDATA{"destdata"};
 const std::string FLAGS{"flags"};
 const std::string HDCHAIN{"hdchain"};
 const std::string KEYMETA{"keymeta"};
 const std::string KEY{"key"};
 const std::string MASTER_KEY{"mkey"};
 const std::string MINVERSION{"minversion"};
 const std::string NAME{"name"};
 const std::string OLD_KEY{"wkey"};
 const std::string ORDERPOSNEXT{"orderposnext"};
 const std::string POOL{"pool"};
 const std::string PURPOSE{"purpose"};
 const std::string SETTINGS{"settings"};
 const std::string TX{"tx"};
 const std::string VERSION{"version"};
 const std::string WALLETDESCRIPTOR{"walletdescriptor"};
 const std::string WALLETDESCRIPTORCACHE{"walletdescriptorcache"};
 const std::string WALLETDESCRIPTORCKEY{"walletdescriptorckey"};
 const std::string WALLETDESCRIPTORKEY{"walletdescriptorkey"};
 const std::string WATCHMETA{"watchmeta"};
 const std::string WATCHS{"watchs"};
 } // namespace DBKeys
 
 //
 // WalletBatch
 //
 
 bool WalletBatch::WriteName(const CTxDestination &address,
                             const std::string &strName) {
     if (!IsValidDestination(address)) {
         return false;
     }
     return WriteIC(
         std::make_pair(DBKeys::NAME, EncodeLegacyAddr(address, Params())),
         strName);
 }
 
 bool WalletBatch::EraseName(const CTxDestination &address) {
     // This should only be used for sending addresses, never for receiving
     // addresses, receiving addresses must always have an address book entry if
     // they're not change return.
     if (!IsValidDestination(address)) {
         return false;
     }
     return EraseIC(
         std::make_pair(DBKeys::NAME, EncodeLegacyAddr(address, Params())));
 }
 
 bool WalletBatch::WritePurpose(const CTxDestination &address,
                                const std::string &strPurpose) {
     if (!IsValidDestination(address)) {
         return false;
     }
     return WriteIC(
         std::make_pair(DBKeys::PURPOSE, EncodeLegacyAddr(address, Params())),
         strPurpose);
 }
 
 bool WalletBatch::ErasePurpose(const CTxDestination &address) {
     if (!IsValidDestination(address)) {
         return false;
     }
     return EraseIC(
         std::make_pair(DBKeys::PURPOSE, EncodeLegacyAddr(address, Params())));
 }
 
 bool WalletBatch::WriteTx(const CWalletTx &wtx) {
     return WriteIC(std::make_pair(DBKeys::TX, wtx.GetId()), wtx);
 }
 
 bool WalletBatch::EraseTx(uint256 hash) {
     return EraseIC(std::make_pair(DBKeys::TX, hash));
 }
 
 bool WalletBatch::WriteKeyMetadata(const CKeyMetadata &meta,
                                    const CPubKey &pubkey,
                                    const bool overwrite) {
     return WriteIC(std::make_pair(DBKeys::KEYMETA, pubkey), meta, overwrite);
 }
 
 bool WalletBatch::WriteKey(const CPubKey &vchPubKey, const CPrivKey &vchPrivKey,
                            const CKeyMetadata &keyMeta) {
     if (!WriteKeyMetadata(keyMeta, vchPubKey, false)) {
         return false;
     }
 
     // hash pubkey/privkey to accelerate wallet load
     std::vector<uint8_t> vchKey;
     vchKey.reserve(vchPubKey.size() + vchPrivKey.size());
     vchKey.insert(vchKey.end(), vchPubKey.begin(), vchPubKey.end());
     vchKey.insert(vchKey.end(), vchPrivKey.begin(), vchPrivKey.end());
 
     return WriteIC(std::make_pair(DBKeys::KEY, vchPubKey),
                    std::make_pair(vchPrivKey, Hash(vchKey)), false);
 }
 
 bool WalletBatch::WriteCryptedKey(const CPubKey &vchPubKey,
                                   const std::vector<uint8_t> &vchCryptedSecret,
                                   const CKeyMetadata &keyMeta) {
     if (!WriteKeyMetadata(keyMeta, vchPubKey, true)) {
         return false;
     }
 
     // Compute a checksum of the encrypted key
     uint256 checksum = Hash(vchCryptedSecret);
 
     const auto key = std::make_pair(DBKeys::CRYPTED_KEY, vchPubKey);
     if (!WriteIC(key, std::make_pair(vchCryptedSecret, checksum), false)) {
         // It may already exist, so try writing just the checksum
         std::vector<uint8_t> val;
         if (!m_batch.Read(key, val)) {
             return false;
         }
         if (!WriteIC(key, std::make_pair(val, checksum), true)) {
             return false;
         }
     }
     EraseIC(std::make_pair(DBKeys::KEY, vchPubKey));
     return true;
 }
 
 bool WalletBatch::WriteMasterKey(unsigned int nID,
                                  const CMasterKey &kMasterKey) {
     return WriteIC(std::make_pair(DBKeys::MASTER_KEY, nID), kMasterKey, true);
 }
 
 bool WalletBatch::WriteCScript(const uint160 &hash,
                                const CScript &redeemScript) {
     return WriteIC(std::make_pair(DBKeys::CSCRIPT, hash), redeemScript, false);
 }
 
 bool WalletBatch::WriteWatchOnly(const CScript &dest,
                                  const CKeyMetadata &keyMeta) {
     if (!WriteIC(std::make_pair(DBKeys::WATCHMETA, dest), keyMeta)) {
         return false;
     }
     return WriteIC(std::make_pair(DBKeys::WATCHS, dest), '1');
 }
 
 bool WalletBatch::EraseWatchOnly(const CScript &dest) {
     if (!EraseIC(std::make_pair(DBKeys::WATCHMETA, dest))) {
         return false;
     }
     return EraseIC(std::make_pair(DBKeys::WATCHS, dest));
 }
 
 bool WalletBatch::WriteBestBlock(const CBlockLocator &locator) {
     // Write empty block locator so versions that require a merkle branch
     // automatically rescan
     WriteIC(DBKeys::BESTBLOCK, CBlockLocator());
     return WriteIC(DBKeys::BESTBLOCK_NOMERKLE, locator);
 }
 
 bool WalletBatch::ReadBestBlock(CBlockLocator &locator) {
     if (m_batch.Read(DBKeys::BESTBLOCK, locator) && !locator.vHave.empty()) {
         return true;
     }
     return m_batch.Read(DBKeys::BESTBLOCK_NOMERKLE, locator);
 }
 
 bool WalletBatch::WriteOrderPosNext(int64_t nOrderPosNext) {
     return WriteIC(DBKeys::ORDERPOSNEXT, nOrderPosNext);
 }
 
 bool WalletBatch::ReadPool(int64_t nPool, CKeyPool &keypool) {
     return m_batch.Read(std::make_pair(DBKeys::POOL, nPool), keypool);
 }
 
 bool WalletBatch::WritePool(int64_t nPool, const CKeyPool &keypool) {
     return WriteIC(std::make_pair(DBKeys::POOL, nPool), keypool);
 }
 
 bool WalletBatch::ErasePool(int64_t nPool) {
     return EraseIC(std::make_pair(DBKeys::POOL, nPool));
 }
 
 bool WalletBatch::WriteMinVersion(int nVersion) {
     return WriteIC(DBKeys::MINVERSION, nVersion);
 }
 
 bool WalletBatch::WriteActiveScriptPubKeyMan(uint8_t type, const uint256 &id,
                                              bool internal) {
     std::string key =
         internal ? DBKeys::ACTIVEINTERNALSPK : DBKeys::ACTIVEEXTERNALSPK;
     return WriteIC(make_pair(key, type), id);
 }
 
 bool WalletBatch::WriteDescriptorKey(const uint256 &desc_id,
                                      const CPubKey &pubkey,
                                      const CPrivKey &privkey) {
     // hash pubkey/privkey to accelerate wallet load
     std::vector<uint8_t> key;
     key.reserve(pubkey.size() + privkey.size());
     key.insert(key.end(), pubkey.begin(), pubkey.end());
     key.insert(key.end(), privkey.begin(), privkey.end());
 
     return WriteIC(std::make_pair(DBKeys::WALLETDESCRIPTORKEY,
                                   std::make_pair(desc_id, pubkey)),
                    std::make_pair(privkey, Hash(key)), false);
 }
 
 bool WalletBatch::WriteCryptedDescriptorKey(
     const uint256 &desc_id, const CPubKey &pubkey,
     const std::vector<uint8_t> &secret) {
     if (!WriteIC(std::make_pair(DBKeys::WALLETDESCRIPTORCKEY,
                                 std::make_pair(desc_id, pubkey)),
                  secret, false)) {
         return false;
     }
     EraseIC(std::make_pair(DBKeys::WALLETDESCRIPTORKEY,
                            std::make_pair(desc_id, pubkey)));
     return true;
 }
 
 bool WalletBatch::WriteDescriptor(const uint256 &desc_id,
                                   const WalletDescriptor &descriptor) {
     return WriteIC(make_pair(DBKeys::WALLETDESCRIPTOR, desc_id), descriptor);
 }
 
 bool WalletBatch::WriteDescriptorDerivedCache(const CExtPubKey &xpub,
                                               const uint256 &desc_id,
                                               uint32_t key_exp_index,
                                               uint32_t der_index) {
     std::vector<uint8_t> ser_xpub(BIP32_EXTKEY_SIZE);
     xpub.Encode(ser_xpub.data());
     return WriteIC(
         std::make_pair(std::make_pair(DBKeys::WALLETDESCRIPTORCACHE, desc_id),
                        std::make_pair(key_exp_index, der_index)),
         ser_xpub);
 }
 
 bool WalletBatch::WriteDescriptorParentCache(const CExtPubKey &xpub,
                                              const uint256 &desc_id,
                                              uint32_t key_exp_index) {
     std::vector<uint8_t> ser_xpub(BIP32_EXTKEY_SIZE);
     xpub.Encode(ser_xpub.data());
     return WriteIC(
         std::make_pair(std::make_pair(DBKeys::WALLETDESCRIPTORCACHE, desc_id),
                        key_exp_index),
         ser_xpub);
 }
 
 class CWalletScanState {
 public:
     unsigned int nKeys{0};
     unsigned int nCKeys{0};
     unsigned int nWatchKeys{0};
     unsigned int nKeyMeta{0};
     unsigned int m_unknown_records{0};
     bool fIsEncrypted{false};
     bool fAnyUnordered{false};
     std::vector<TxId> vWalletUpgrade;
     std::map<OutputType, uint256> m_active_external_spks;
     std::map<OutputType, uint256> m_active_internal_spks;
     std::map<uint256, DescriptorCache> m_descriptor_caches;
     std::map<std::pair<uint256, CKeyID>, CKey> m_descriptor_keys;
     std::map<std::pair<uint256, CKeyID>,
              std::pair<CPubKey, std::vector<uint8_t>>>
         m_descriptor_crypt_keys;
     std::map<uint160, CHDChain> m_hd_chains;
 
     CWalletScanState() {}
 };
 
 static bool ReadKeyValue(CWallet *pwallet, CDataStream &ssKey,
                          CDataStream &ssValue, CWalletScanState &wss,
                          std::string &strType, std::string &strErr)
     EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
     try {
         // Unserialize
         // Taking advantage of the fact that pair serialization is just the two
         // items serialized one after the other.
         ssKey >> strType;
         if (strType == DBKeys::NAME) {
             std::string strAddress;
             ssKey >> strAddress;
             std::string label;
             ssValue >> label;
             pwallet
                 ->m_address_book[DecodeDestination(strAddress,
                                                    pwallet->GetChainParams())]
                 .SetLabel(label);
         } else if (strType == DBKeys::PURPOSE) {
             std::string strAddress;
             ssKey >> strAddress;
             ssValue >> pwallet
                            ->m_address_book[DecodeDestination(
                                strAddress, pwallet->GetChainParams())]
                            .purpose;
         } else if (strType == DBKeys::TX) {
             TxId txid;
             ssKey >> txid;
             // LoadToWallet call below creates a new CWalletTx that fill_wtx
             // callback fills with transaction metadata.
             auto fill_wtx = [&](CWalletTx &wtx, bool new_tx) {
                 assert(new_tx);
                 ssValue >> wtx;
                 if (wtx.GetId() != txid) {
                     return false;
                 }
 
                 // Undo serialize changes in 31600
                 if (31404 <= wtx.fTimeReceivedIsTxTime &&
                     wtx.fTimeReceivedIsTxTime <= 31703) {
                     if (!ssValue.empty()) {
                         char fTmp;
                         char fUnused;
                         std::string unused_string;
                         ssValue >> fTmp >> fUnused >> unused_string;
                         strErr = strprintf(
                             "LoadWallet() upgrading tx ver=%d %d %s",
                             wtx.fTimeReceivedIsTxTime, fTmp, txid.ToString());
                         wtx.fTimeReceivedIsTxTime = fTmp;
                     } else {
                         strErr = strprintf(
                             "LoadWallet() repairing tx ver=%d %s",
                             wtx.fTimeReceivedIsTxTime, txid.ToString());
                         wtx.fTimeReceivedIsTxTime = 0;
                     }
                     wss.vWalletUpgrade.push_back(txid);
                 }
 
                 if (wtx.nOrderPos == -1) {
                     wss.fAnyUnordered = true;
                 }
 
                 return true;
             };
             if (!pwallet->LoadToWallet(txid, fill_wtx)) {
                 return false;
             }
         } else if (strType == DBKeys::WATCHS) {
             wss.nWatchKeys++;
             CScript script;
             ssKey >> script;
             char fYes;
             ssValue >> fYes;
             if (fYes == '1') {
                 pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadWatchOnly(
                     script);
             }
         } else if (strType == DBKeys::KEY) {
             CPubKey vchPubKey;
             ssKey >> vchPubKey;
             if (!vchPubKey.IsValid()) {
                 strErr = "Error reading wallet database: CPubKey corrupt";
                 return false;
             }
             CKey key;
             CPrivKey pkey;
             uint256 hash;
 
             wss.nKeys++;
             ssValue >> pkey;
 
             // Old wallets store keys as DBKeys::KEY [pubkey] => [privkey] ...
             // which was slow for wallets with lots of keys, because the public
             // key is re-derived from the private key using EC operations as a
             // checksum. Newer wallets store keys as DBKeys::KEY [pubkey] =>
             // [privkey][hash(pubkey,privkey)], which is much faster while
             // remaining backwards-compatible.
             try {
                 ssValue >> hash;
             } catch (...) {
             }
 
             bool fSkipCheck = false;
 
             if (!hash.IsNull()) {
                 // hash pubkey/privkey to accelerate wallet load
                 std::vector<uint8_t> vchKey;
                 vchKey.reserve(vchPubKey.size() + pkey.size());
                 vchKey.insert(vchKey.end(), vchPubKey.begin(), vchPubKey.end());
                 vchKey.insert(vchKey.end(), pkey.begin(), pkey.end());
 
                 if (Hash(vchKey) != hash) {
                     strErr = "Error reading wallet database: CPubKey/CPrivKey "
                              "corrupt";
                     return false;
                 }
 
                 fSkipCheck = true;
             }
 
             if (!key.Load(pkey, vchPubKey, fSkipCheck)) {
                 strErr = "Error reading wallet database: CPrivKey corrupt";
                 return false;
             }
             if (!pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadKey(
                     key, vchPubKey)) {
                 strErr = "Error reading wallet database: "
                          "LegacyScriptPubKeyMan::LoadKey failed";
                 return false;
             }
         } else if (strType == DBKeys::MASTER_KEY) {
             // Master encryption key is loaded into only the wallet and not any
             // of the ScriptPubKeyMans.
             unsigned int nID;
             ssKey >> nID;
             CMasterKey kMasterKey;
             ssValue >> kMasterKey;
             if (pwallet->mapMasterKeys.count(nID) != 0) {
                 strErr = strprintf(
                     "Error reading wallet database: duplicate CMasterKey id %u",
                     nID);
                 return false;
             }
             pwallet->mapMasterKeys[nID] = kMasterKey;
             if (pwallet->nMasterKeyMaxID < nID) {
                 pwallet->nMasterKeyMaxID = nID;
             }
         } else if (strType == DBKeys::CRYPTED_KEY) {
             CPubKey vchPubKey;
             ssKey >> vchPubKey;
             if (!vchPubKey.IsValid()) {
                 strErr = "Error reading wallet database: CPubKey corrupt";
                 return false;
             }
             std::vector<uint8_t> vchPrivKey;
             ssValue >> vchPrivKey;
 
             // Get the checksum and check it
             bool checksum_valid = false;
             if (!ssValue.eof()) {
                 uint256 checksum;
                 ssValue >> checksum;
                 if ((checksum_valid = Hash(vchPrivKey) != checksum)) {
                     strErr =
                         "Error reading wallet database: Crypted key corrupt";
                     return false;
                 }
             }
 
             wss.nCKeys++;
 
             if (!pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadCryptedKey(
                     vchPubKey, vchPrivKey, checksum_valid)) {
                 strErr = "Error reading wallet database: "
                          "LegacyScriptPubKeyMan::LoadCryptedKey failed";
                 return false;
             }
             wss.fIsEncrypted = true;
         } else if (strType == DBKeys::KEYMETA) {
             CPubKey vchPubKey;
             ssKey >> vchPubKey;
             CKeyMetadata keyMeta;
             ssValue >> keyMeta;
             wss.nKeyMeta++;
             pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadKeyMetadata(
                 vchPubKey.GetID(), keyMeta);
 
             // Extract some CHDChain info from this metadata if it has any
             if (keyMeta.nVersion >= CKeyMetadata::VERSION_WITH_HDDATA &&
                 !keyMeta.hd_seed_id.IsNull() && keyMeta.hdKeypath.size() > 0) {
                 // Get the path from the key origin or from the path string
                 // Not applicable when path is "s" or "m" as those indicate a
                 // seed.
                 // See https://reviews.bitcoinabc.org/D4175
                 bool internal = false;
                 uint32_t index = 0;
                 if (keyMeta.hdKeypath != "s" && keyMeta.hdKeypath != "m") {
                     std::vector<uint32_t> path;
                     if (keyMeta.has_key_origin) {
                         // We have a key origin, so pull it from its path vector
                         path = keyMeta.key_origin.path;
                     } else {
                         // No key origin, have to parse the string
                         if (!ParseHDKeypath(keyMeta.hdKeypath, path)) {
                             strErr = "Error reading wallet database: keymeta "
                                      "with invalid HD keypath";
                             return false;
                         }
                     }
 
                     // Extract the index and internal from the path
                     // Path string is m/0'/k'/i'
                     // Path vector is [0', k', i'] (but as ints OR'd with the
                     // hardened bit k == 0 for external, 1 for internal. i is
                     // the index
                     if (path.size() != 3) {
                         strErr = "Error reading wallet database: keymeta found "
                                  "with unexpected path";
                         return false;
                     }
                     if (path[0] != 0x80000000) {
                         strErr = strprintf(
                             "Unexpected path index of 0x%08x (expected "
                             "0x80000000) for the element at index 0",
                             path[0]);
                         return false;
                     }
                     if (path[1] != 0x80000000 && path[1] != (1 | 0x80000000)) {
                         strErr =
                             strprintf("Unexpected path index of 0x%08x "
                                       "(expected 0x80000000 or 0x80000001) for "
                                       "the element at index 1",
                                       path[1]);
                         return false;
                     }
                     if ((path[2] & 0x80000000) == 0) {
                         strErr = strprintf(
                             "Unexpected path index of 0x%08x (expected to be "
                             "greater than or equal to 0x80000000)",
                             path[2]);
                         return false;
                     }
                     internal = path[1] == (1 | 0x80000000);
                     index = path[2] & ~0x80000000;
                 }
 
                 // Insert a new CHDChain, or get the one that already exists
                 auto ins =
                     wss.m_hd_chains.emplace(keyMeta.hd_seed_id, CHDChain());
                 CHDChain &chain = ins.first->second;
                 if (ins.second) {
                     // For new chains, we want to default to VERSION_HD_BASE
                     // until we see an internal
                     chain.nVersion = CHDChain::VERSION_HD_BASE;
                     chain.seed_id = keyMeta.hd_seed_id;
                 }
                 if (internal) {
                     chain.nVersion = CHDChain::VERSION_HD_CHAIN_SPLIT;
                     chain.nInternalChainCounter =
                         std::max(chain.nInternalChainCounter, index);
                 } else {
                     chain.nExternalChainCounter =
                         std::max(chain.nExternalChainCounter, index);
                 }
             }
         } else if (strType == DBKeys::WATCHMETA) {
             CScript script;
             ssKey >> script;
             CKeyMetadata keyMeta;
             ssValue >> keyMeta;
             wss.nKeyMeta++;
             pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadScriptMetadata(
                 CScriptID(script), keyMeta);
         } else if (strType == DBKeys::DEFAULTKEY) {
             // We don't want or need the default key, but if there is one set,
             // we want to make sure that it is valid so that we can detect
             // corruption
             CPubKey vchPubKey;
             ssValue >> vchPubKey;
             if (!vchPubKey.IsValid()) {
                 strErr = "Error reading wallet database: Default Key corrupt";
                 return false;
             }
         } else if (strType == DBKeys::POOL) {
             int64_t nIndex;
             ssKey >> nIndex;
             CKeyPool keypool;
             ssValue >> keypool;
 
             pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadKeyPool(nIndex,
                                                                      keypool);
         } else if (strType == DBKeys::CSCRIPT) {
             uint160 hash;
             ssKey >> hash;
             CScript script;
             ssValue >> script;
             if (!pwallet->GetOrCreateLegacyScriptPubKeyMan()->LoadCScript(
                     script)) {
                 strErr = "Error reading wallet database: "
                          "LegacyScriptPubKeyMan::LoadCScript failed";
                 return false;
             }
         } else if (strType == DBKeys::ORDERPOSNEXT) {
             ssValue >> pwallet->nOrderPosNext;
         } else if (strType == DBKeys::DESTDATA) {
             std::string strAddress, strKey, strValue;
             ssKey >> strAddress;
             ssKey >> strKey;
             ssValue >> strValue;
             pwallet->LoadDestData(
                 DecodeDestination(strAddress, pwallet->GetChainParams()),
                 strKey, strValue);
         } else if (strType == DBKeys::HDCHAIN) {
             CHDChain chain;
             ssValue >> chain;
             pwallet->GetOrCreateLegacyScriptPubKeyMan()->SetHDChain(chain,
                                                                     true);
         } else if (strType == DBKeys::FLAGS) {
             uint64_t flags;
             ssValue >> flags;
             if (!pwallet->SetWalletFlags(flags, true)) {
                 strErr = "Error reading wallet database: Unknown non-tolerable "
                          "wallet flags found";
                 return false;
             }
         } else if (strType == DBKeys::OLD_KEY) {
             strErr = "Found unsupported 'wkey' record, try loading with "
                      "version 0.20";
             return false;
         } else if (strType == DBKeys::ACTIVEEXTERNALSPK ||
                    strType == DBKeys::ACTIVEINTERNALSPK) {
             uint8_t type;
             ssKey >> type;
             uint256 id;
             ssValue >> id;
 
             bool internal = strType == DBKeys::ACTIVEINTERNALSPK;
             auto &spk_mans = internal ? wss.m_active_internal_spks
                                       : wss.m_active_external_spks;
             if (spk_mans.count(static_cast<OutputType>(type)) > 0) {
                 strErr =
                     "Multiple ScriptPubKeyMans specified for a single type";
                 return false;
             }
             spk_mans[static_cast<OutputType>(type)] = id;
         } else if (strType == DBKeys::WALLETDESCRIPTOR) {
             uint256 id;
             ssKey >> id;
             WalletDescriptor desc;
             ssValue >> desc;
             if (wss.m_descriptor_caches.count(id) == 0) {
                 wss.m_descriptor_caches[id] = DescriptorCache();
             }
             pwallet->LoadDescriptorScriptPubKeyMan(id, desc);
         } else if (strType == DBKeys::WALLETDESCRIPTORCACHE) {
             bool parent = true;
             uint256 desc_id;
             uint32_t key_exp_index;
             uint32_t der_index;
             ssKey >> desc_id;
             ssKey >> key_exp_index;
 
             // if the der_index exists, it's a derived xpub
             try {
                 ssKey >> der_index;
                 parent = false;
             } catch (...) {
             }
 
             std::vector<uint8_t> ser_xpub(BIP32_EXTKEY_SIZE);
             ssValue >> ser_xpub;
             CExtPubKey xpub;
             xpub.Decode(ser_xpub.data());
             if (wss.m_descriptor_caches.count(desc_id)) {
                 wss.m_descriptor_caches[desc_id] = DescriptorCache();
             }
             if (parent) {
                 wss.m_descriptor_caches[desc_id].CacheParentExtPubKey(
                     key_exp_index, xpub);
             } else {
                 wss.m_descriptor_caches[desc_id].CacheDerivedExtPubKey(
                     key_exp_index, der_index, xpub);
             }
         } else if (strType == DBKeys::WALLETDESCRIPTORKEY) {
             uint256 desc_id;
             CPubKey pubkey;
             ssKey >> desc_id;
             ssKey >> pubkey;
             if (!pubkey.IsValid()) {
                 strErr = "Error reading wallet database: CPubKey corrupt";
                 return false;
             }
             CKey key;
             CPrivKey pkey;
             uint256 hash;
 
             wss.nKeys++;
             ssValue >> pkey;
             ssValue >> hash;
 
             // hash pubkey/privkey to accelerate wallet load
             std::vector<uint8_t> to_hash;
             to_hash.reserve(pubkey.size() + pkey.size());
             to_hash.insert(to_hash.end(), pubkey.begin(), pubkey.end());
             to_hash.insert(to_hash.end(), pkey.begin(), pkey.end());
 
             if (Hash(to_hash) != hash) {
                 strErr =
                     "Error reading wallet database: CPubKey/CPrivKey corrupt";
                 return false;
             }
 
             if (!key.Load(pkey, pubkey, true)) {
                 strErr = "Error reading wallet database: CPrivKey corrupt";
                 return false;
             }
             wss.m_descriptor_keys.insert(
                 std::make_pair(std::make_pair(desc_id, pubkey.GetID()), key));
         } else if (strType == DBKeys::WALLETDESCRIPTORCKEY) {
             uint256 desc_id;
             CPubKey pubkey;
             ssKey >> desc_id;
             ssKey >> pubkey;
             if (!pubkey.IsValid()) {
                 strErr = "Error reading wallet database: CPubKey corrupt";
                 return false;
             }
             std::vector<uint8_t> privkey;
             ssValue >> privkey;
             wss.nCKeys++;
 
             wss.m_descriptor_crypt_keys.insert(
                 std::make_pair(std::make_pair(desc_id, pubkey.GetID()),
                                std::make_pair(pubkey, privkey)));
             wss.fIsEncrypted = true;
         } else if (strType != DBKeys::BESTBLOCK &&
                    strType != DBKeys::BESTBLOCK_NOMERKLE &&
                    strType != DBKeys::MINVERSION &&
                    strType != DBKeys::ACENTRY && strType != DBKeys::VERSION &&
                    strType != DBKeys::SETTINGS) {
             wss.m_unknown_records++;
         }
     } catch (const std::exception &e) {
         if (strErr.empty()) {
             strErr = e.what();
         }
         return false;
     } catch (...) {
         if (strErr.empty()) {
             strErr = "Caught unknown exception in ReadKeyValue";
         }
         return false;
     }
     return true;
 }
 
 bool ReadKeyValue(CWallet *pwallet, CDataStream &ssKey, CDataStream &ssValue,
                   std::string &strType, std::string &strErr) {
     CWalletScanState dummy_wss;
     LOCK(pwallet->cs_wallet);
     return ReadKeyValue(pwallet, ssKey, ssValue, dummy_wss, strType, strErr);
 }
 
 bool WalletBatch::IsKeyType(const std::string &strType) {
     return (strType == DBKeys::KEY || strType == DBKeys::MASTER_KEY ||
             strType == DBKeys::CRYPTED_KEY);
 }
 
 DBErrors WalletBatch::LoadWallet(CWallet *pwallet) {
     CWalletScanState wss;
     bool fNoncriticalErrors = false;
     DBErrors result = DBErrors::LOAD_OK;
 
     LOCK(pwallet->cs_wallet);
     try {
         int nMinVersion = 0;
         if (m_batch.Read(DBKeys::MINVERSION, nMinVersion)) {
             if (nMinVersion > FEATURE_LATEST) {
                 return DBErrors::TOO_NEW;
             }
             pwallet->LoadMinVersion(nMinVersion);
         }
 
         // Get cursor
         Dbc *pcursor = m_batch.GetCursor();
         if (!pcursor) {
             pwallet->WalletLogPrintf("Error getting wallet database cursor\n");
             return DBErrors::CORRUPT;
         }
 
         while (true) {
             // Read next record
             CDataStream ssKey(SER_DISK, CLIENT_VERSION);
             CDataStream ssValue(SER_DISK, CLIENT_VERSION);
             int ret = m_batch.ReadAtCursor(pcursor, ssKey, ssValue);
             if (ret == DB_NOTFOUND) {
                 break;
             }
 
             if (ret != 0) {
                 pwallet->WalletLogPrintf(
                     "Error reading next record from wallet database\n");
                 return DBErrors::CORRUPT;
             }
 
             // Try to be tolerant of single corrupt records:
             std::string strType, strErr;
             if (!ReadKeyValue(pwallet, ssKey, ssValue, wss, strType, strErr)) {
                 // losing keys is considered a catastrophic error, anything else
                 // we assume the user can live with:
                 if (IsKeyType(strType) || strType == DBKeys::DEFAULTKEY) {
                     result = DBErrors::CORRUPT;
                 } else if (strType == DBKeys::FLAGS) {
                     // Reading the wallet flags can only fail if unknown flags
                     // are present.
                     result = DBErrors::TOO_NEW;
                 } else {
                     // Leave other errors alone, if we try to fix them we might
                     // make things worse. But do warn the user there is
                     // something wrong.
                     fNoncriticalErrors = true;
                     if (strType == DBKeys::TX) {
                         // Rescan if there is a bad transaction record:
                         gArgs.SoftSetBoolArg("-rescan", true);
                     }
                 }
             }
             if (!strErr.empty()) {
                 pwallet->WalletLogPrintf("%s\n", strErr);
             }
         }
         pcursor->close();
     } catch (...) {
         result = DBErrors::CORRUPT;
     }
 
     // Set the active ScriptPubKeyMans
     for (auto spk_man_pair : wss.m_active_external_spks) {
         pwallet->SetActiveScriptPubKeyMan(
             spk_man_pair.second, spk_man_pair.first, /* internal */ false,
             /* memonly */ true);
     }
     for (auto spk_man_pair : wss.m_active_internal_spks) {
         pwallet->SetActiveScriptPubKeyMan(
             spk_man_pair.second, spk_man_pair.first, /* internal */ true,
             /* memonly */ true);
     }
 
     // Set the descriptor caches
     for (auto desc_cache_pair : wss.m_descriptor_caches) {
         auto spk_man = pwallet->GetScriptPubKeyMan(desc_cache_pair.first);
         assert(spk_man);
         ((DescriptorScriptPubKeyMan *)spk_man)
             ->SetCache(desc_cache_pair.second);
     }
 
     // Set the descriptor keys
     for (auto desc_key_pair : wss.m_descriptor_keys) {
         auto spk_man = pwallet->GetScriptPubKeyMan(desc_key_pair.first.first);
         ((DescriptorScriptPubKeyMan *)spk_man)
             ->AddKey(desc_key_pair.first.second, desc_key_pair.second);
     }
     for (auto desc_key_pair : wss.m_descriptor_crypt_keys) {
         auto spk_man = pwallet->GetScriptPubKeyMan(desc_key_pair.first.first);
         ((DescriptorScriptPubKeyMan *)spk_man)
             ->AddCryptedKey(desc_key_pair.first.second,
                             desc_key_pair.second.first,
                             desc_key_pair.second.second);
     }
 
     if (fNoncriticalErrors && result == DBErrors::LOAD_OK) {
         result = DBErrors::NONCRITICAL_ERROR;
     }
 
     // Any wallet corruption at all: skip any rewriting or upgrading, we don't
     // want to make it worse.
     if (result != DBErrors::LOAD_OK) {
         return result;
     }
 
     // Last client version to open this wallet, was previously the file version
     // number
     int last_client = CLIENT_VERSION;
     m_batch.Read(DBKeys::VERSION, last_client);
 
     int wallet_version = pwallet->GetVersion();
     pwallet->WalletLogPrintf("Wallet File Version = %d\n",
                              wallet_version > 0 ? wallet_version : last_client);
 
     pwallet->WalletLogPrintf("Keys: %u plaintext, %u encrypted, %u w/ "
                              "metadata, %u total. Unknown wallet records: %u\n",
                              wss.nKeys, wss.nCKeys, wss.nKeyMeta,
                              wss.nKeys + wss.nCKeys, wss.m_unknown_records);
 
     // nTimeFirstKey is only reliable if all keys have metadata
     if (pwallet->IsLegacy() &&
         (wss.nKeys + wss.nCKeys + wss.nWatchKeys) != wss.nKeyMeta) {
         auto spk_man = pwallet->GetOrCreateLegacyScriptPubKeyMan();
         if (spk_man) {
             LOCK(spk_man->cs_KeyStore);
             spk_man->UpdateTimeFirstKey(1);
         }
     }
 
     for (const TxId &txid : wss.vWalletUpgrade) {
         WriteTx(pwallet->mapWallet.at(txid));
     }
 
     // Rewrite encrypted wallets of versions 0.4.0 and 0.5.0rc:
     if (wss.fIsEncrypted && (last_client == 40000 || last_client == 50000)) {
         return DBErrors::NEED_REWRITE;
     }
 
     if (last_client < CLIENT_VERSION) {
         // Update
         m_batch.Write(DBKeys::VERSION, CLIENT_VERSION);
     }
 
     if (wss.fAnyUnordered) {
         result = pwallet->ReorderTransactions();
     }
 
     // Upgrade all of the wallet keymetadata to have the hd master key id
     // This operation is not atomic, but if it fails, updated entries are still
     // backwards compatible with older software
     try {
         pwallet->UpgradeKeyMetadata();
     } catch (...) {
         result = DBErrors::CORRUPT;
     }
 
     // Set the inactive chain
     if (wss.m_hd_chains.size() > 0) {
         LegacyScriptPubKeyMan *legacy_spkm =
             pwallet->GetLegacyScriptPubKeyMan();
         if (!legacy_spkm) {
             pwallet->WalletLogPrintf(
                 "Inactive HD Chains found but no Legacy ScriptPubKeyMan\n");
             return DBErrors::CORRUPT;
         }
         for (const auto &chain_pair : wss.m_hd_chains) {
             if (chain_pair.first !=
                 pwallet->GetLegacyScriptPubKeyMan()->GetHDChain().seed_id) {
                 pwallet->GetLegacyScriptPubKeyMan()->AddInactiveHDChain(
                     chain_pair.second);
             }
         }
     }
 
     return result;
 }
 
 DBErrors WalletBatch::FindWalletTx(std::vector<TxId> &txIds,
                                    std::list<CWalletTx> &vWtx) {
     DBErrors result = DBErrors::LOAD_OK;
 
     try {
         int nMinVersion = 0;
         if (m_batch.Read(DBKeys::MINVERSION, nMinVersion)) {
             if (nMinVersion > FEATURE_LATEST) {
                 return DBErrors::TOO_NEW;
             }
         }
 
         // Get cursor
         Dbc *pcursor = m_batch.GetCursor();
         if (!pcursor) {
             LogPrintf("Error getting wallet database cursor\n");
             return DBErrors::CORRUPT;
         }
 
         while (true) {
             // Read next record
             CDataStream ssKey(SER_DISK, CLIENT_VERSION);
             CDataStream ssValue(SER_DISK, CLIENT_VERSION);
             int ret = m_batch.ReadAtCursor(pcursor, ssKey, ssValue);
             if (ret == DB_NOTFOUND) {
                 break;
             }
 
             if (ret != 0) {
                 LogPrintf("Error reading next record from wallet database\n");
                 return DBErrors::CORRUPT;
             }
 
             std::string strType;
             ssKey >> strType;
             if (strType == DBKeys::TX) {
                 TxId txid;
                 ssKey >> txid;
                 txIds.push_back(txid);
                 vWtx.emplace_back(nullptr /* wallet */, nullptr /* tx */);
                 ssValue >> vWtx.back();
             }
         }
         pcursor->close();
     } catch (...) {
         result = DBErrors::CORRUPT;
     }
 
     return result;
 }
 
 DBErrors WalletBatch::ZapSelectTx(std::vector<TxId> &txIdsIn,
                                   std::vector<TxId> &txIdsOut) {
     // Build list of wallet TXs and hashes.
     std::vector<TxId> txIds;
     std::list<CWalletTx> vWtx;
     DBErrors err = FindWalletTx(txIds, vWtx);
     if (err != DBErrors::LOAD_OK) {
         return err;
     }
 
     std::sort(txIds.begin(), txIds.end());
     std::sort(txIdsIn.begin(), txIdsIn.end());
 
     // Erase each matching wallet TX.
     bool delerror = false;
     std::vector<TxId>::iterator it = txIdsIn.begin();
     for (const TxId &txid : txIds) {
         while (it < txIdsIn.end() && (*it) < txid) {
             it++;
         }
         if (it == txIdsIn.end()) {
             break;
         }
 
         if ((*it) == txid) {
             if (!EraseTx(txid)) {
                 LogPrint(BCLog::WALLETDB,
                          "Transaction was found for deletion but returned "
                          "database error: %s\n",
                          txid.GetHex());
                 delerror = true;
             }
             txIdsOut.push_back(txid);
         }
     }
 
     if (delerror) {
         return DBErrors::CORRUPT;
     }
     return DBErrors::LOAD_OK;
 }
 
 DBErrors WalletBatch::ZapWalletTx(std::list<CWalletTx> &vWtx) {
     // Build list of wallet TXs.
     std::vector<TxId> txIds;
     DBErrors err = FindWalletTx(txIds, vWtx);
     if (err != DBErrors::LOAD_OK) {
         return err;
     }
 
     // Erase each wallet TX.
     for (const TxId &txid : txIds) {
         if (!EraseTx(txid)) {
             return DBErrors::CORRUPT;
         }
     }
 
     return DBErrors::LOAD_OK;
 }
 
 void MaybeCompactWalletDB() {
     static std::atomic<bool> fOneThread;
     if (fOneThread.exchange(true)) {
         return;
     }
 
     for (const std::shared_ptr<CWallet> &pwallet : GetWallets()) {
         WalletDatabase &dbh = pwallet->GetDBHandle();
 
         unsigned int nUpdateCounter = dbh.nUpdateCounter;
 
         if (dbh.nLastSeen != nUpdateCounter) {
             dbh.nLastSeen = nUpdateCounter;
             dbh.nLastWalletUpdate = GetTime();
         }
 
         if (dbh.nLastFlushed != nUpdateCounter &&
             GetTime() - dbh.nLastWalletUpdate >= 2) {
             if (dbh.PeriodicFlush()) {
                 dbh.nLastFlushed = nUpdateCounter;
             }
         }
     }
 
     fOneThread = false;
 }
 
 bool WalletBatch::WriteDestData(const CTxDestination &address,
                                 const std::string &key,
                                 const std::string &value) {
     if (!IsValidDestination(address)) {
         return false;
     }
     return WriteIC(
         std::make_pair(
             DBKeys::DESTDATA,
             std::make_pair(EncodeLegacyAddr(address, Params()), key)),
         value);
 }
 
 bool WalletBatch::EraseDestData(const CTxDestination &address,
                                 const std::string &key) {
     if (!IsValidDestination(address)) {
         return false;
     }
     return EraseIC(std::make_pair(
         DBKeys::DESTDATA,
         std::make_pair(EncodeLegacyAddr(address, Params()), key)));
 }
 
 bool WalletBatch::WriteHDChain(const CHDChain &chain) {
     return WriteIC(DBKeys::HDCHAIN, chain);
 }
 
 bool WalletBatch::WriteWalletFlags(const uint64_t flags) {
     return WriteIC(DBKeys::FLAGS, flags);
 }
 
 bool WalletBatch::TxnBegin() {
     return m_batch.TxnBegin();
 }
 
 bool WalletBatch::TxnCommit() {
     return m_batch.TxnCommit();
 }
 
 bool WalletBatch::TxnAbort() {
     return m_batch.TxnAbort();
 }
 
 bool IsWalletLoaded(const fs::path &wallet_path) {
     return IsBDBWalletLoaded(wallet_path);
 }
+
+/** Return object for accessing database at specified path. */
+std::unique_ptr<BerkeleyDatabase> CreateWalletDatabase(const fs::path &path) {
+    std::string filename;
+    return std::make_unique<BerkeleyDatabase>(GetWalletEnv(path, filename),
+                                              std::move(filename));
+}
+
+/**
+ * Return object for accessing dummy database with no read/write capabilities.
+ */
+std::unique_ptr<BerkeleyDatabase> CreateDummyWalletDatabase() {
+    return std::make_unique<BerkeleyDatabase>();
+}
+
+/** Return object for accessing temporary in-memory database. */
+std::unique_ptr<BerkeleyDatabase> CreateMockWalletDatabase() {
+    return std::make_unique<BerkeleyDatabase>(
+        std::make_shared<BerkeleyEnvironment>(), "");
+}
diff --git a/src/wallet/walletdb.h b/src/wallet/walletdb.h
index ef72b891a..4696a57de 100644
--- a/src/wallet/walletdb.h
+++ b/src/wallet/walletdb.h
@@ -1,312 +1,323 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Copyright (c) 2017-2020 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_WALLET_WALLETDB_H
 #define BITCOIN_WALLET_WALLETDB_H
 
 #include <amount.h>
 #include <key.h>
 #include <script/sign.h>
 #include <script/standard.h> // for CTxDestination
 #include <wallet/bdb.h>
 #include <wallet/walletutil.h>
 
 #include <cstdint>
 #include <string>
 #include <vector>
 
 /**
  * Overview of wallet database classes:
  *
  * - WalletBatch is an abstract modifier object for the wallet database, and
  * encapsulates a database batch update as well as methods to act on the
  * database. It should be agnostic to the database implementation.
  *
  * The following classes are implementation specific:
  * - BerkeleyEnvironment is an environment in which the database exists.
  * - BerkeleyDatabase represents a wallet database.
  * - BerkeleyBatch is a low-level database batch update.
  */
 
 static const bool DEFAULT_FLUSHWALLET = true;
 
 struct CBlockLocator;
 class CKeyPool;
 class CMasterKey;
 class CScript;
 class CWallet;
 class CWalletTx;
 class uint160;
 class uint256;
 
 /** Backend-agnostic database type. */
 using WalletDatabase = BerkeleyDatabase;
 
 /** Error statuses for the wallet database */
 enum class DBErrors {
     LOAD_OK,
     CORRUPT,
     NONCRITICAL_ERROR,
     TOO_NEW,
     LOAD_FAIL,
     NEED_REWRITE
 };
 
 namespace DBKeys {
 extern const std::string ACENTRY;
 extern const std::string ACTIVEEXTERNALSPK;
 extern const std::string ACTIVEINTERNALSPK;
 extern const std::string BESTBLOCK;
 extern const std::string BESTBLOCK_NOMERKLE;
 extern const std::string CRYPTED_KEY;
 extern const std::string CSCRIPT;
 extern const std::string DEFAULTKEY;
 extern const std::string DESTDATA;
 extern const std::string FLAGS;
 extern const std::string HDCHAIN;
 extern const std::string KEY;
 extern const std::string KEYMETA;
 extern const std::string MASTER_KEY;
 extern const std::string MINVERSION;
 extern const std::string NAME;
 extern const std::string OLD_KEY;
 extern const std::string ORDERPOSNEXT;
 extern const std::string POOL;
 extern const std::string PURPOSE;
 extern const std::string SETTINGS;
 extern const std::string TX;
 extern const std::string VERSION;
 extern const std::string WALLETDESCRIPTOR;
 extern const std::string WALLETDESCRIPTORCACHE;
 extern const std::string WALLETDESCRIPTORCKEY;
 extern const std::string WALLETDESCRIPTORKEY;
 extern const std::string WATCHMETA;
 extern const std::string WATCHS;
 } // namespace DBKeys
 
 /* simple HD chain data model */
 class CHDChain {
 public:
     uint32_t nExternalChainCounter;
     uint32_t nInternalChainCounter;
     //! seed hash160
     CKeyID seed_id;
 
     static const int VERSION_HD_BASE = 1;
     static const int VERSION_HD_CHAIN_SPLIT = 2;
     static const int CURRENT_VERSION = VERSION_HD_CHAIN_SPLIT;
     int nVersion;
 
     CHDChain() { SetNull(); }
 
     SERIALIZE_METHODS(CHDChain, obj) {
         READWRITE(obj.nVersion, obj.nExternalChainCounter, obj.seed_id);
         if (obj.nVersion >= VERSION_HD_CHAIN_SPLIT) {
             READWRITE(obj.nInternalChainCounter);
         }
     }
 
     void SetNull() {
         nVersion = CHDChain::CURRENT_VERSION;
         nExternalChainCounter = 0;
         nInternalChainCounter = 0;
         seed_id.SetNull();
     }
 
     bool operator==(const CHDChain &chain) const {
         return seed_id == chain.seed_id;
     }
 };
 
 class CKeyMetadata {
 public:
     static const int VERSION_BASIC = 1;
     static const int VERSION_WITH_HDDATA = 10;
     static const int VERSION_WITH_KEY_ORIGIN = 12;
     static const int CURRENT_VERSION = VERSION_WITH_KEY_ORIGIN;
     int nVersion;
     // 0 means unknown.
     int64_t nCreateTime;
     // optional HD/bip32 keypath. Still used to determine whether a key is a
     // seed. Also kept for backwards compatibility
     std::string hdKeypath;
     // Id of the HD seed used to derive this key.
     CKeyID hd_seed_id;
     // Key origin info with path and fingerprint
     KeyOriginInfo key_origin;
     //! Whether the key_origin is useful
     bool has_key_origin = false;
 
     CKeyMetadata() { SetNull(); }
     explicit CKeyMetadata(int64_t nCreateTime_) {
         SetNull();
         nCreateTime = nCreateTime_;
     }
 
     SERIALIZE_METHODS(CKeyMetadata, obj) {
         READWRITE(obj.nVersion, obj.nCreateTime);
         if (obj.nVersion >= VERSION_WITH_HDDATA) {
             READWRITE(obj.hdKeypath, obj.hd_seed_id);
         }
         if (obj.nVersion >= VERSION_WITH_KEY_ORIGIN) {
             READWRITE(obj.key_origin);
             READWRITE(obj.has_key_origin);
         }
     }
 
     void SetNull() {
         nVersion = CKeyMetadata::CURRENT_VERSION;
         nCreateTime = 0;
         hdKeypath.clear();
         hd_seed_id.SetNull();
         key_origin.clear();
         has_key_origin = false;
     }
 };
 
 /**
  * Access to the wallet database.
  * Opens the database and provides read and write access to it. Each read and
  * write is its own transaction. Multiple operation transactions can be started
  * using TxnBegin() and committed using TxnCommit() Otherwise the transaction
  * will be committed when the object goes out of scope. Optionally (on by
  * default) it will flush to disk on close. Every 1000 writes will automatically
  * trigger a flush to disk.
  */
 class WalletBatch {
 private:
     template <typename K, typename T>
     bool WriteIC(const K &key, const T &value, bool fOverwrite = true) {
         if (!m_batch.Write(key, value, fOverwrite)) {
             return false;
         }
         m_database.IncrementUpdateCounter();
         if (m_database.nUpdateCounter % 1000 == 0) {
             m_batch.Flush();
         }
         return true;
     }
 
     template <typename K> bool EraseIC(const K &key) {
         if (!m_batch.Erase(key)) {
             return false;
         }
         m_database.IncrementUpdateCounter();
         if (m_database.nUpdateCounter % 1000 == 0) {
             m_batch.Flush();
         }
         return true;
     }
 
 public:
     explicit WalletBatch(WalletDatabase &database, const char *pszMode = "r+",
                          bool _fFlushOnClose = true)
         : m_batch(database, pszMode, _fFlushOnClose), m_database(database) {}
     WalletBatch(const WalletBatch &) = delete;
     WalletBatch &operator=(const WalletBatch &) = delete;
 
     bool WriteName(const CTxDestination &address, const std::string &strName);
     bool EraseName(const CTxDestination &address);
 
     bool WritePurpose(const CTxDestination &address,
                       const std::string &purpose);
     bool ErasePurpose(const CTxDestination &address);
 
     bool WriteTx(const CWalletTx &wtx);
     bool EraseTx(uint256 hash);
 
     bool WriteKeyMetadata(const CKeyMetadata &meta, const CPubKey &pubkey,
                           const bool overwrite);
     bool WriteKey(const CPubKey &vchPubKey, const CPrivKey &vchPrivKey,
                   const CKeyMetadata &keyMeta);
     bool WriteCryptedKey(const CPubKey &vchPubKey,
                          const std::vector<uint8_t> &vchCryptedSecret,
                          const CKeyMetadata &keyMeta);
     bool WriteMasterKey(unsigned int nID, const CMasterKey &kMasterKey);
 
     bool WriteCScript(const uint160 &hash, const CScript &redeemScript);
 
     bool WriteWatchOnly(const CScript &script, const CKeyMetadata &keymeta);
     bool EraseWatchOnly(const CScript &script);
 
     bool WriteBestBlock(const CBlockLocator &locator);
     bool ReadBestBlock(CBlockLocator &locator);
 
     bool WriteOrderPosNext(int64_t nOrderPosNext);
 
     bool ReadPool(int64_t nPool, CKeyPool &keypool);
     bool WritePool(int64_t nPool, const CKeyPool &keypool);
     bool ErasePool(int64_t nPool);
 
     bool WriteMinVersion(int nVersion);
 
     bool WriteDescriptorKey(const uint256 &desc_id, const CPubKey &pubkey,
                             const CPrivKey &privkey);
     bool WriteCryptedDescriptorKey(const uint256 &desc_id,
                                    const CPubKey &pubkey,
                                    const std::vector<uint8_t> &secret);
     bool WriteDescriptor(const uint256 &desc_id,
                          const WalletDescriptor &descriptor);
     bool WriteDescriptorDerivedCache(const CExtPubKey &xpub,
                                      const uint256 &desc_id,
                                      uint32_t key_exp_index,
                                      uint32_t der_index);
     bool WriteDescriptorParentCache(const CExtPubKey &xpub,
                                     const uint256 &desc_id,
                                     uint32_t key_exp_index);
 
     /// Write destination data key,value tuple to database.
     bool WriteDestData(const CTxDestination &address, const std::string &key,
                        const std::string &value);
     /// Erase destination data tuple from wallet database.
     bool EraseDestData(const CTxDestination &address, const std::string &key);
 
     bool WriteActiveScriptPubKeyMan(uint8_t type, const uint256 &id,
                                     bool internal);
 
     DBErrors LoadWallet(CWallet *pwallet);
     DBErrors FindWalletTx(std::vector<TxId> &txIds, std::list<CWalletTx> &vWtx);
     DBErrors ZapWalletTx(std::list<CWalletTx> &vWtx);
     DBErrors ZapSelectTx(std::vector<TxId> &txIdsIn,
                          std::vector<TxId> &txIdsOut);
     /* Function to determine if a certain KV/key-type is a key (cryptographical
      * key) type */
     static bool IsKeyType(const std::string &strType);
     /* verifies the database environment */
     static bool VerifyEnvironment(const fs::path &wallet_path,
                                   bilingual_str &errorStr);
     /* verifies the database file */
     static bool VerifyDatabaseFile(const fs::path &wallet_path,
                                    bilingual_str &errorStr);
 
     //! write the hdchain model (external chain child index counter)
     bool WriteHDChain(const CHDChain &chain);
 
     bool WriteWalletFlags(const uint64_t flags);
     //! Begin a new transaction
     bool TxnBegin();
     //! Commit current transaction
     bool TxnCommit();
     //! Abort current transaction
     bool TxnAbort();
 
 private:
     BerkeleyBatch m_batch;
     WalletDatabase &m_database;
 };
 
 //! Compacts BDB state so that wallet.dat is self-contained (if there are
 //! changes)
 void MaybeCompactWalletDB();
 
 //! Unserialize a given Key-Value pair and load it into the wallet
 bool ReadKeyValue(CWallet *pwallet, CDataStream &ssKey, CDataStream &ssValue,
                   std::string &strType, std::string &strErr);
 
 /** Return whether a wallet database is currently loaded. */
 bool IsWalletLoaded(const fs::path &wallet_path);
 
+/** Return object for accessing database at specified path. */
+std::unique_ptr<BerkeleyDatabase> CreateWalletDatabase(const fs::path &path);
+
+/**
+ * Return object for accessing dummy database with no read/write capabilities.
+ */
+std::unique_ptr<BerkeleyDatabase> CreateDummyWalletDatabase();
+
+/** Return object for accessing temporary in-memory database. */
+std::unique_ptr<BerkeleyDatabase> CreateMockWalletDatabase();
+
 #endif // BITCOIN_WALLET_WALLETDB_H