diff --git a/src/txdb.cpp b/src/txdb.cpp
index 0ea7d4baf8..38d3772dc6 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -1,631 +1,617 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <txdb.h>
 
 #include <chainparams.h>
 #include <hash.h>
 #include <init.h>
 #include <pow.h>
 #include <random.h>
 #include <ui_interface.h>
 #include <uint256.h>
 #include <util.h>
 
 #include <boost/thread.hpp> // boost::this_thread::interruption_point() (mingw)
 
 #include <cstdint>
 
 static const char DB_COIN = 'C';
 static const char DB_COINS = 'c';
 static const char DB_BLOCK_FILES = 'f';
 static const char DB_TXINDEX = 't';
 static const char DB_TXINDEX_BLOCK = 'T';
 static const char DB_BLOCK_INDEX = 'b';
 
 static const char DB_BEST_BLOCK = 'B';
 static const char DB_HEAD_BLOCKS = 'H';
 static const char DB_FLAG = 'F';
 static const char DB_REINDEX_FLAG = 'R';
 static const char DB_LAST_BLOCK = 'l';
 
 namespace {
 
 struct CoinEntry {
     COutPoint *outpoint;
     char key;
     explicit CoinEntry(const COutPoint *ptr)
         : outpoint(const_cast<COutPoint *>(ptr)), key(DB_COIN) {}
 
     template <typename Stream> void Serialize(Stream &s) const {
         s << key;
         s << outpoint->GetTxId();
         s << VARINT(outpoint->GetN());
     }
 
     template <typename Stream> void Unserialize(Stream &s) {
         s >> key;
         uint256 id;
         s >> id;
         uint32_t n = 0;
         s >> VARINT(n);
         *outpoint = COutPoint(id, n);
     }
 };
 } // namespace
 
 CCoinsViewDB::CCoinsViewDB(size_t nCacheSize, bool fMemory, bool fWipe)
     : db(GetDataDir() / "chainstate", nCacheSize, fMemory, fWipe, true) {}
 
 bool CCoinsViewDB::GetCoin(const COutPoint &outpoint, Coin &coin) const {
     return db.Read(CoinEntry(&outpoint), coin);
 }
 
 bool CCoinsViewDB::HaveCoin(const COutPoint &outpoint) const {
     return db.Exists(CoinEntry(&outpoint));
 }
 
 uint256 CCoinsViewDB::GetBestBlock() const {
     uint256 hashBestChain;
     if (!db.Read(DB_BEST_BLOCK, hashBestChain)) return uint256();
     return hashBestChain;
 }
 
 std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {
     std::vector<uint256> vhashHeadBlocks;
     if (!db.Read(DB_HEAD_BLOCKS, vhashHeadBlocks)) {
         return std::vector<uint256>();
     }
     return vhashHeadBlocks;
 }
 
 bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
     CDBBatch batch(db);
     size_t count = 0;
     size_t changed = 0;
     size_t batch_size =
         (size_t)gArgs.GetArg("-dbbatchsize", nDefaultDbBatchSize);
     int crash_simulate = gArgs.GetArg("-dbcrashratio", 0);
     assert(!hashBlock.IsNull());
 
     uint256 old_tip = GetBestBlock();
     if (old_tip.IsNull()) {
         // We may be in the middle of replaying.
         std::vector<uint256> old_heads = GetHeadBlocks();
         if (old_heads.size() == 2) {
             assert(old_heads[0] == hashBlock);
             old_tip = old_heads[1];
         }
     }
 
     // In the first batch, mark the database as being in the middle of a
     // transition from old_tip to hashBlock.
     // A vector is used for future extensibility, as we may want to support
     // interrupting after partial writes from multiple independent reorgs.
     batch.Erase(DB_BEST_BLOCK);
     batch.Write(DB_HEAD_BLOCKS, std::vector<uint256>{hashBlock, old_tip});
 
     for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
         if (it->second.flags & CCoinsCacheEntry::DIRTY) {
             CoinEntry entry(&it->first);
             if (it->second.coin.IsSpent()) {
                 batch.Erase(entry);
             } else {
                 batch.Write(entry, it->second.coin);
             }
             changed++;
         }
         count++;
         CCoinsMap::iterator itOld = it++;
         mapCoins.erase(itOld);
         if (batch.SizeEstimate() > batch_size) {
             LogPrint(BCLog::COINDB, "Writing partial batch of %.2f MiB\n",
                      batch.SizeEstimate() * (1.0 / 1048576.0));
             db.WriteBatch(batch);
             batch.Clear();
             if (crash_simulate) {
                 static FastRandomContext rng;
                 if (rng.randrange(crash_simulate) == 0) {
                     LogPrintf("Simulating a crash. Goodbye.\n");
                     _Exit(0);
                 }
             }
         }
     }
 
     // In the last batch, mark the database as consistent with hashBlock again.
     batch.Erase(DB_HEAD_BLOCKS);
     batch.Write(DB_BEST_BLOCK, hashBlock);
 
     LogPrint(BCLog::COINDB, "Writing final batch of %.2f MiB\n",
              batch.SizeEstimate() * (1.0 / 1048576.0));
     bool ret = db.WriteBatch(batch);
     LogPrint(BCLog::COINDB,
              "Committed %u changed transaction outputs (out of "
              "%u) to coin database...\n",
              (unsigned int)changed, (unsigned int)count);
     return ret;
 }
 
 size_t CCoinsViewDB::EstimateSize() const {
     return db.EstimateSize(DB_COIN, char(DB_COIN + 1));
 }
 
 CBlockTreeDB::CBlockTreeDB(size_t nCacheSize, bool fMemory, bool fWipe)
     : CDBWrapper(gArgs.IsArgSet("-blocksdir")
                      ? GetDataDir() / "blocks" / "index"
                      : GetBlocksDir() / "index",
                  nCacheSize, fMemory, fWipe) {}
 
 bool CBlockTreeDB::ReadBlockFileInfo(int nFile, CBlockFileInfo &info) {
     return Read(std::make_pair(DB_BLOCK_FILES, nFile), info);
 }
 
 bool CBlockTreeDB::WriteReindexing(bool fReindexing) {
     if (fReindexing)
         return Write(DB_REINDEX_FLAG, '1');
     else
         return Erase(DB_REINDEX_FLAG);
 }
 
 bool CBlockTreeDB::ReadReindexing(bool &fReindexing) {
     fReindexing = Exists(DB_REINDEX_FLAG);
     return true;
 }
 
 bool CBlockTreeDB::ReadLastBlockFile(int &nFile) {
     return Read(DB_LAST_BLOCK, nFile);
 }
 
 CCoinsViewCursor *CCoinsViewDB::Cursor() const {
     CCoinsViewDBCursor *i = new CCoinsViewDBCursor(
         const_cast<CDBWrapper &>(db).NewIterator(), GetBestBlock());
     /**
      * It seems that there are no "const iterators" for LevelDB. Since we only
      * need read operations on it, use a const-cast to get around that
      * restriction.
      */
     i->pcursor->Seek(DB_COIN);
     // Cache key of first record
     if (i->pcursor->Valid()) {
         CoinEntry entry(&i->keyTmp.second);
         i->pcursor->GetKey(entry);
         i->keyTmp.first = entry.key;
     } else {
         // Make sure Valid() and GetKey() return false
         i->keyTmp.first = 0;
     }
     return i;
 }
 
 bool CCoinsViewDBCursor::GetKey(COutPoint &key) const {
     // Return cached key
     if (keyTmp.first == DB_COIN) {
         key = keyTmp.second;
         return true;
     }
     return false;
 }
 
 bool CCoinsViewDBCursor::GetValue(Coin &coin) const {
     return pcursor->GetValue(coin);
 }
 
 unsigned int CCoinsViewDBCursor::GetValueSize() const {
     return pcursor->GetValueSize();
 }
 
 bool CCoinsViewDBCursor::Valid() const {
     return keyTmp.first == DB_COIN;
 }
 
 void CCoinsViewDBCursor::Next() {
     pcursor->Next();
     CoinEntry entry(&keyTmp.second);
     if (!pcursor->Valid() || !pcursor->GetKey(entry)) {
         // Invalidate cached key after last record so that Valid() and GetKey()
         // return false
         keyTmp.first = 0;
     } else {
         keyTmp.first = entry.key;
     }
 }
 
 bool CBlockTreeDB::WriteBatchSync(
     const std::vector<std::pair<int, const CBlockFileInfo *>> &fileInfo,
     int nLastFile, const std::vector<const CBlockIndex *> &blockinfo) {
     CDBBatch batch(*this);
     for (std::vector<std::pair<int, const CBlockFileInfo *>>::const_iterator
              it = fileInfo.begin();
          it != fileInfo.end(); it++) {
         batch.Write(std::make_pair(DB_BLOCK_FILES, it->first), *it->second);
     }
     batch.Write(DB_LAST_BLOCK, nLastFile);
     for (std::vector<const CBlockIndex *>::const_iterator it =
              blockinfo.begin();
          it != blockinfo.end(); it++) {
         batch.Write(std::make_pair(DB_BLOCK_INDEX, (*it)->GetBlockHash()),
                     CDiskBlockIndex(*it));
     }
     return WriteBatch(batch, true);
 }
 
-bool CBlockTreeDB::ReadTxIndex(const uint256 &txid, CDiskTxPos &pos) {
-    return Read(std::make_pair(DB_TXINDEX, txid), pos);
-}
-
-bool CBlockTreeDB::WriteTxIndex(
-    const std::vector<std::pair<uint256, CDiskTxPos>> &vect) {
-    CDBBatch batch(*this);
-    for (std::vector<std::pair<uint256, CDiskTxPos>>::const_iterator it =
-             vect.begin();
-         it != vect.end(); it++)
-        batch.Write(std::make_pair(DB_TXINDEX, it->first), it->second);
-    return WriteBatch(batch);
-}
-
 bool CBlockTreeDB::WriteFlag(const std::string &name, bool fValue) {
     return Write(std::make_pair(DB_FLAG, name), fValue ? '1' : '0');
 }
 
 bool CBlockTreeDB::ReadFlag(const std::string &name, bool &fValue) {
     char ch;
     if (!Read(std::make_pair(DB_FLAG, name), ch)) return false;
     fValue = ch == '1';
     return true;
 }
 
 bool CBlockTreeDB::LoadBlockIndexGuts(
     const Config &config,
     std::function<CBlockIndex *(const uint256 &)> insertBlockIndex) {
 
     std::unique_ptr<CDBIterator> pcursor(NewIterator());
 
     pcursor->Seek(std::make_pair(DB_BLOCK_INDEX, uint256()));
 
     // Load mapBlockIndex
     while (pcursor->Valid()) {
         boost::this_thread::interruption_point();
         std::pair<char, uint256> key;
         if (!pcursor->GetKey(key) || key.first != DB_BLOCK_INDEX) {
             break;
         }
 
         CDiskBlockIndex diskindex;
         if (!pcursor->GetValue(diskindex)) {
             return error("LoadBlockIndex() : failed to read value");
         }
 
         // Construct block index object
         CBlockIndex *pindexNew = insertBlockIndex(diskindex.GetBlockHash());
         pindexNew->pprev = insertBlockIndex(diskindex.hashPrev);
         pindexNew->nHeight = diskindex.nHeight;
         pindexNew->nFile = diskindex.nFile;
         pindexNew->nDataPos = diskindex.nDataPos;
         pindexNew->nUndoPos = diskindex.nUndoPos;
         pindexNew->nVersion = diskindex.nVersion;
         pindexNew->hashMerkleRoot = diskindex.hashMerkleRoot;
         pindexNew->nTime = diskindex.nTime;
         pindexNew->nBits = diskindex.nBits;
         pindexNew->nNonce = diskindex.nNonce;
         pindexNew->nStatus = diskindex.nStatus;
         pindexNew->nTx = diskindex.nTx;
 
         if (!CheckProofOfWork(pindexNew->GetBlockHash(), pindexNew->nBits,
                               config)) {
             return error("LoadBlockIndex(): CheckProofOfWork failed: %s",
                          pindexNew->ToString());
         }
 
         pcursor->Next();
     }
 
     return true;
 }
 
 namespace {
 //! Legacy class to deserialize pre-pertxout database entries without reindex.
 class CCoins {
 public:
     //! whether transaction is a coinbase
     bool fCoinBase;
 
     //! unspent transaction outputs; spent outputs are .IsNull(); spent outputs
     //! at the end of the array are dropped
     std::vector<CTxOut> vout;
 
     //! at which height this transaction was included in the active block chain
     int nHeight;
 
     //! empty constructor
     CCoins() : fCoinBase(false), vout(0), nHeight(0) {}
 
     template <typename Stream> void Unserialize(Stream &s) {
         uint32_t nCode = 0;
         // version
         int nVersionDummy;
         ::Unserialize(s, VARINT(nVersionDummy));
         // header code
         ::Unserialize(s, VARINT(nCode));
         fCoinBase = nCode & 1;
         std::vector<bool> vAvail(2, false);
         vAvail[0] = (nCode & 2) != 0;
         vAvail[1] = (nCode & 4) != 0;
         uint32_t nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
         // spentness bitmask
         while (nMaskCode > 0) {
             uint8_t chAvail = 0;
             ::Unserialize(s, chAvail);
             for (unsigned int p = 0; p < 8; p++) {
                 bool f = (chAvail & (1 << p)) != 0;
                 vAvail.push_back(f);
             }
             if (chAvail != 0) {
                 nMaskCode--;
             }
         }
         // txouts themself
         vout.assign(vAvail.size(), CTxOut());
         for (size_t i = 0; i < vAvail.size(); i++) {
             if (vAvail[i]) {
                 ::Unserialize(s, CTxOutCompressor(vout[i]));
             }
         }
         // coinbase height
         ::Unserialize(s, VARINT(nHeight));
     }
 };
 } // namespace
 
 /**
  * Upgrade the database from older formats.
  *
  * Currently implemented: from the per-tx utxo model (0.8..0.14.x) to per-txout.
  */
 bool CCoinsViewDB::Upgrade() {
     std::unique_ptr<CDBIterator> pcursor(db.NewIterator());
     pcursor->Seek(std::make_pair(DB_COINS, uint256()));
     if (!pcursor->Valid()) {
         return true;
     }
 
     int64_t count = 0;
     LogPrintf("Upgrading utxo-set database...\n");
     LogPrintf("[0%%]...");
     uiInterface.ShowProgress(_("Upgrading UTXO database"), 0, true);
     size_t batch_size = 1 << 24;
     CDBBatch batch(db);
     int reportDone = 0;
     std::pair<uint8_t, uint256> key;
     std::pair<uint8_t, uint256> prev_key = {DB_COINS, uint256()};
     while (pcursor->Valid()) {
         boost::this_thread::interruption_point();
         if (ShutdownRequested()) {
             break;
         }
 
         if (!pcursor->GetKey(key) || key.first != DB_COINS) {
             break;
         }
 
         if (count++ % 256 == 0) {
             uint32_t high =
                 0x100 * *key.second.begin() + *(key.second.begin() + 1);
             int percentageDone = (int)(high * 100.0 / 65536.0 + 0.5);
             uiInterface.ShowProgress(_("Upgrading UTXO database"),
                                      percentageDone, true);
             if (reportDone < percentageDone / 10) {
                 // report max. every 10% step
                 LogPrintf("[%d%%]...", percentageDone);
                 reportDone = percentageDone / 10;
             }
         }
 
         CCoins old_coins;
         if (!pcursor->GetValue(old_coins)) {
             return error("%s: cannot parse CCoins record", __func__);
         }
 
         TxId id(key.second);
         for (size_t i = 0; i < old_coins.vout.size(); ++i) {
             if (!old_coins.vout[i].IsNull() &&
                 !old_coins.vout[i].scriptPubKey.IsUnspendable()) {
                 Coin newcoin(std::move(old_coins.vout[i]), old_coins.nHeight,
                              old_coins.fCoinBase);
                 COutPoint outpoint(id, i);
                 CoinEntry entry(&outpoint);
                 batch.Write(entry, newcoin);
             }
         }
 
         batch.Erase(key);
         if (batch.SizeEstimate() > batch_size) {
             db.WriteBatch(batch);
             batch.Clear();
             db.CompactRange(prev_key, key);
             prev_key = key;
         }
 
         pcursor->Next();
     }
 
     db.WriteBatch(batch);
     db.CompactRange({DB_COINS, uint256()}, key);
     uiInterface.ShowProgress("", 100, false);
     LogPrintf("[%s].\n", ShutdownRequested() ? "CANCELLED" : "DONE");
     return !ShutdownRequested();
 }
 
 TxIndexDB::TxIndexDB(size_t n_cache_size, bool f_memory, bool f_wipe)
     : CDBWrapper(GetDataDir() / "indexes" / "txindex", n_cache_size, f_memory,
                  f_wipe) {}
 
 bool TxIndexDB::ReadTxPos(const uint256 &txid, CDiskTxPos &pos) const {
     return Read(std::make_pair(DB_TXINDEX, txid), pos);
 }
 
 bool TxIndexDB::WriteTxs(
     const std::vector<std::pair<uint256, CDiskTxPos>> &v_pos) {
     CDBBatch batch(*this);
     for (const auto &tuple : v_pos) {
         batch.Write(std::make_pair(DB_TXINDEX, tuple.first), tuple.second);
     }
     return WriteBatch(batch);
 }
 
 bool TxIndexDB::ReadBestBlock(CBlockLocator &locator) const {
     bool success = Read(DB_BEST_BLOCK, locator);
     if (!success) {
         locator.SetNull();
     }
     return success;
 }
 
 bool TxIndexDB::WriteBestBlock(const CBlockLocator &locator) {
     return Write(DB_BEST_BLOCK, locator);
 }
 
 /*
  * Safely persist a transfer of data from the old txindex database to the new
  * one, and compact the range of keys updated. This is used internally by
  * MigrateData.
  */
 static void
 WriteTxIndexMigrationBatches(TxIndexDB &newdb, CBlockTreeDB &olddb,
                              CDBBatch &batch_newdb, CDBBatch &batch_olddb,
                              const std::pair<unsigned char, uint256> &begin_key,
                              const std::pair<unsigned char, uint256> &end_key) {
     // Sync new DB changes to disk before deleting from old DB.
     newdb.WriteBatch(batch_newdb, /*fSync=*/true);
     olddb.WriteBatch(batch_olddb);
     olddb.CompactRange(begin_key, end_key);
 
     batch_newdb.Clear();
     batch_olddb.Clear();
 }
 
 bool TxIndexDB::MigrateData(CBlockTreeDB &block_tree_db,
                             const CBlockLocator &best_locator) {
     // The prior implementation of txindex was always in sync with block index
     // and presence was indicated with a boolean DB flag. If the flag is set,
     // this means the txindex from a previous version is valid and in sync with
     // the chain tip. The first step of the migration is to unset the flag and
     // write the chain hash to a separate key, DB_TXINDEX_BLOCK. After that, the
     // index entries are copied over in batches to the new database. Finally,
     // DB_TXINDEX_BLOCK is erased from the old database and the block hash is
     // written to the new database.
     //
     // Unsetting the boolean flag ensures that if the node is downgraded to a
     // previous version, it will not see a corrupted, partially migrated index
     // -- it will see that the txindex is disabled. When the node is upgraded
     // again, the migration will pick up where it left off and sync to the block
     // with hash DB_TXINDEX_BLOCK.
     bool f_legacy_flag = false;
     block_tree_db.ReadFlag("txindex", f_legacy_flag);
     if (f_legacy_flag) {
         if (!block_tree_db.Write(DB_TXINDEX_BLOCK, best_locator)) {
             return error("%s: cannot write block indicator", __func__);
         }
         if (!block_tree_db.WriteFlag("txindex", false)) {
             return error("%s: cannot write block index db flag", __func__);
         }
     }
 
     CBlockLocator locator;
     if (!block_tree_db.Read(DB_TXINDEX_BLOCK, locator)) {
         return true;
     }
 
     int64_t count = 0;
     LogPrintf("Upgrading txindex database... [0%%]\n");
     uiInterface.InitMessage(_("Upgrading txindex database"));
     uiInterface.ShowProgress(_("Upgrading txindex database"), 0, true);
     int report_done = 0;
     const size_t batch_size = 1 << 24; // 16 MiB
 
     CDBBatch batch_newdb(*this);
     CDBBatch batch_olddb(block_tree_db);
 
     std::pair<unsigned char, uint256> key;
     std::pair<unsigned char, uint256> begin_key{DB_TXINDEX, uint256()};
     std::pair<unsigned char, uint256> prev_key = begin_key;
 
     bool interrupted = false;
     std::unique_ptr<CDBIterator> cursor(block_tree_db.NewIterator());
     for (cursor->Seek(begin_key); cursor->Valid(); cursor->Next()) {
         boost::this_thread::interruption_point();
         if (ShutdownRequested()) {
             interrupted = true;
             break;
         }
 
         if (!cursor->GetKey(key)) {
             return error("%s: cannot get key from valid cursor", __func__);
         }
         if (key.first != DB_TXINDEX) {
             break;
         }
 
         // Log progress every 10%.
         if (++count % 256 == 0) {
             // Since txids are uniformly random and traversed in increasing
             // order, the high 16 bits of the hash can be used to estimate the
             // current progress.
             const uint256 &txid = key.second;
             uint32_t high_nibble =
                 (static_cast<uint32_t>(*(txid.begin() + 0)) << 8) +
                 (static_cast<uint32_t>(*(txid.begin() + 1)) << 0);
             int percentage_done = (int)(high_nibble * 100.0 / 65536.0 + 0.5);
 
             uiInterface.ShowProgress(_("Upgrading txindex database"),
                                      percentage_done, true);
             if (report_done < percentage_done / 10) {
                 LogPrintf("Upgrading txindex database... [%d%%]\n",
                           percentage_done);
                 report_done = percentage_done / 10;
             }
         }
 
         CDiskTxPos value;
         if (!cursor->GetValue(value)) {
             return error("%s: cannot parse txindex record", __func__);
         }
         batch_newdb.Write(key, value);
         batch_olddb.Erase(key);
 
         if (batch_newdb.SizeEstimate() > batch_size ||
             batch_olddb.SizeEstimate() > batch_size) {
             // NOTE: it's OK to delete the key pointed at by the current DB
             // cursor while iterating because LevelDB iterators are guaranteed
             // to provide a consistent view of the underlying data, like a
             // lightweight snapshot.
             WriteTxIndexMigrationBatches(*this, block_tree_db, batch_newdb,
                                          batch_olddb, prev_key, key);
             prev_key = key;
         }
     }
 
     // If these final DB batches complete the migration, write the best block
     // hash marker to the new database and delete from the old one. This signals
     // that the former is fully caught up to that point in the blockchain and
     // that all txindex entries have been removed from the latter.
     if (!interrupted) {
         batch_olddb.Erase(DB_TXINDEX_BLOCK);
         batch_newdb.Write(DB_BEST_BLOCK, locator);
     }
 
     WriteTxIndexMigrationBatches(*this, block_tree_db, batch_newdb, batch_olddb,
                                  begin_key, key);
 
     if (interrupted) {
         LogPrintf("[CANCELLED].\n");
         return false;
     }
 
     uiInterface.ShowProgress("", 100, false);
 
     LogPrintf("[DONE].\n");
     return true;
 }
diff --git a/src/txdb.h b/src/txdb.h
index e19912dadf..a4591e0c7a 100644
--- a/src/txdb.h
+++ b/src/txdb.h
@@ -1,166 +1,164 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_TXDB_H
 #define BITCOIN_TXDB_H
 
 #include <blockfileinfo.h>
 #include <chain.h>
 #include <coins.h>
 #include <dbwrapper.h>
 #include <diskblockpos.h>
 #include <primitives/block.h>
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
 
 class CBlockIndex;
 class CCoinsViewDBCursor;
 class uint256;
 class Config;
 
 //! No need to periodic flush if at least this much space still available.
 static constexpr int MAX_BLOCK_COINSDB_USAGE = 10;
 //! -dbcache default (MiB)
 static const int64_t nDefaultDbCache = 450;
 //! -dbbatchsize default (bytes)
 static const int64_t nDefaultDbBatchSize = 16 << 20;
 //! max. -dbcache (MiB)
 static const int64_t nMaxDbCache = sizeof(void *) > 4 ? 16384 : 1024;
 //! min. -dbcache (MiB)
 static const int64_t nMinDbCache = 4;
 //! Max memory allocated to block tree DB specific cache, if no -txindex (MiB)
 static const int64_t nMaxBlockDBCache = 2;
 //! Max memory allocated to block tree DB specific cache, if -txindex (MiB)
 // Unlike for the UTXO database, for the txindex scenario the leveldb cache make
 // a meaningful difference:
 // https://github.com/bitcoin/bitcoin/pull/8273#issuecomment-229601991
 static const int64_t nMaxTxIndexCache = 1024;
 //! Max memory allocated to coin DB specific cache (MiB)
 static const int64_t nMaxCoinsDBCache = 8;
 
 struct CDiskTxPos : public CDiskBlockPos {
     unsigned int nTxOffset; // after header
 
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream &s, Operation ser_action) {
         READWRITEAS(CDiskBlockPos, *this);
         READWRITE(VARINT(nTxOffset));
     }
 
     CDiskTxPos(const CDiskBlockPos &blockIn, unsigned int nTxOffsetIn)
         : CDiskBlockPos(blockIn.nFile, blockIn.nPos), nTxOffset(nTxOffsetIn) {}
 
     CDiskTxPos() { SetNull(); }
 
     void SetNull() {
         CDiskBlockPos::SetNull();
         nTxOffset = 0;
     }
 };
 
 /** CCoinsView backed by the coin database (chainstate/) */
 class CCoinsViewDB final : public CCoinsView {
 protected:
     CDBWrapper db;
 
 public:
     explicit CCoinsViewDB(size_t nCacheSize, bool fMemory = false,
                           bool fWipe = false);
 
     bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
     bool HaveCoin(const COutPoint &outpoint) const override;
     uint256 GetBestBlock() const override;
     std::vector<uint256> GetHeadBlocks() const override;
     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
     CCoinsViewCursor *Cursor() const override;
 
     //! Attempt to update from an older database format.
     //! Returns whether an error occurred.
     bool Upgrade();
     size_t EstimateSize() const override;
 };
 
 /** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */
 class CCoinsViewDBCursor : public CCoinsViewCursor {
 public:
     ~CCoinsViewDBCursor() {}
 
     bool GetKey(COutPoint &key) const override;
     bool GetValue(Coin &coin) const override;
     unsigned int GetValueSize() const override;
 
     bool Valid() const override;
     void Next() override;
 
 private:
     CCoinsViewDBCursor(CDBIterator *pcursorIn, const uint256 &hashBlockIn)
         : CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
     std::unique_ptr<CDBIterator> pcursor;
     std::pair<char, COutPoint> keyTmp;
 
     friend class CCoinsViewDB;
 };
 
 /** Access to the block database (blocks/index/) */
 class CBlockTreeDB : public CDBWrapper {
 public:
     explicit CBlockTreeDB(size_t nCacheSize, bool fMemory = false,
                           bool fWipe = false);
 
     bool WriteBatchSync(
         const std::vector<std::pair<int, const CBlockFileInfo *>> &fileInfo,
         int nLastFile, const std::vector<const CBlockIndex *> &blockinfo);
     bool ReadBlockFileInfo(int nFile, CBlockFileInfo &info);
     bool ReadLastBlockFile(int &nFile);
     bool WriteReindexing(bool fReindexing);
     bool ReadReindexing(bool &fReindexing);
-    bool ReadTxIndex(const uint256 &txid, CDiskTxPos &pos);
-    bool WriteTxIndex(const std::vector<std::pair<uint256, CDiskTxPos>> &vect);
     bool WriteFlag(const std::string &name, bool fValue);
     bool ReadFlag(const std::string &name, bool &fValue);
     bool LoadBlockIndexGuts(
         const Config &config,
         std::function<CBlockIndex *(const uint256 &)> insertBlockIndex);
 };
 
 /**
  * Access to the txindex database (indexes/txindex/)
  *
  * The database stores a block locator of the chain the database is synced to
  * so that the TxIndex can efficiently determine the point it last stopped at.
  * A locator is used instead of a simple hash of the chain tip because blocks
  * and block index entries may not be flushed to disk until after this database
  * is updated.
  */
 class TxIndexDB : public CDBWrapper {
 public:
     explicit TxIndexDB(size_t n_cache_size, bool f_memory = false,
                        bool f_wipe = false);
 
     /// Read the disk location of the transaction data with the given hash.
     /// Returns false if the transaction hash is not indexed.
     bool ReadTxPos(const uint256 &txid, CDiskTxPos &pos) const;
 
     /// Write a batch of transaction positions to the DB.
     bool WriteTxs(const std::vector<std::pair<uint256, CDiskTxPos>> &v_pos);
 
     /// Read block locator of the chain that the txindex is in sync with.
     bool ReadBestBlock(CBlockLocator &locator) const;
 
     /// Write block locator of the chain that the txindex is in sync with.
     bool WriteBestBlock(const CBlockLocator &locator);
 
     /// Migrate txindex data from the block tree DB, where it may be for older
     /// nodes that have not been upgraded yet to the new database.
     bool MigrateData(CBlockTreeDB &block_tree_db,
                      const CBlockLocator &best_locator);
 };
 
 #endif // BITCOIN_TXDB_H