Moved BlockchainDB into its own src/ subfolder

Ostensibly janitorial work, but should be more relevant later down the
line.  Things that depend on core cryptonote things (i.e.
    cryptonote_core) don't necessarily depend on BlockchainDB and thus
have no need to have BlockchainDB baked in with them.

2 files changed, 2122 insertions, 0 deletions

diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
new file mode 100644
index 000000000..feff4a272
--- /dev/null
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -0,0 +1,1808 @@
+// Copyright (c) 2014, The Monero Project
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "db_lmdb.h"
+
+#include <boost/filesystem.hpp>
+#include <memory>  // std::unique_ptr
+#include <cstring>  // memcpy
+
+#include "cryptonote_core/cryptonote_format_utils.h"
+#include "crypto/crypto.h"
+#include "profile_tools.h"
+
+using epee::string_tools::pod_to_hex;
+
+namespace
+{
+
+template <typename T>
+inline void throw0(const T &e)
+{
+  LOG_PRINT_L0(e.what());
+  throw e;
+}
+
+template <typename T>
+inline void throw1(const T &e)
+{
+  LOG_PRINT_L1(e.what());
+  throw e;
+}
+
+//  cursor needs to be closed when it goes out of scope,
+//  this helps if the function using it throws
+struct lmdb_cur
+{
+  lmdb_cur(MDB_txn* txn, MDB_dbi dbi)
+  {
+    if (mdb_cursor_open(txn, dbi, &m_cur))
+      throw0(cryptonote::DB_ERROR("Error opening db cursor"));
+    done = false;
+  }
+
+  ~lmdb_cur() { close(); }
+
+  operator MDB_cursor*() { return m_cur; }
+  operator MDB_cursor**() { return &m_cur; }
+
+  void close()
+  {
+    if (!done)
+    {
+      mdb_cursor_close(m_cur);
+      done = true;
+    }
+  }
+
+private:
+  MDB_cursor* m_cur;
+  bool done;
+};
+
+template<typename T>
+struct MDB_val_copy: public MDB_val
+{
+  MDB_val_copy(const T &t): t_copy(t)
+  {
+    mv_size = sizeof (T);
+    mv_data = &t_copy;
+  }
+private:
+  T t_copy;
+};
+
+template<>
+struct MDB_val_copy<cryptonote::blobdata>: public MDB_val
+{
+  MDB_val_copy(const cryptonote::blobdata &bd): data(new char[bd.size()])
+  {
+    memcpy(data.get(), bd.data(), bd.size());
+    mv_size = bd.size();
+    mv_data = data.get();
+  }
+private:
+  std::unique_ptr<char[]> data;
+};
+
+auto compare_uint64 = [](const MDB_val *a, const MDB_val *b) {
+  const uint64_t va = *(const uint64_t*)a->mv_data;
+  const uint64_t vb = *(const uint64_t*)b->mv_data;
+  if (va < vb) return -1;
+  else if (va == vb) return 0;
+  else return 1;
+};
+
+const char* const LMDB_BLOCKS = "blocks";
+const char* const LMDB_BLOCK_TIMESTAMPS = "block_timestamps";
+const char* const LMDB_BLOCK_HEIGHTS = "block_heights";
+const char* const LMDB_BLOCK_HASHES = "block_hashes";
+const char* const LMDB_BLOCK_SIZES = "block_sizes";
+const char* const LMDB_BLOCK_DIFFS = "block_diffs";
+const char* const LMDB_BLOCK_COINS = "block_coins";
+
+const char* const LMDB_TXS = "txs";
+const char* const LMDB_TX_UNLOCKS = "tx_unlocks";
+const char* const LMDB_TX_HEIGHTS = "tx_heights";
+const char* const LMDB_TX_OUTPUTS = "tx_outputs";
+
+const char* const LMDB_OUTPUT_TXS = "output_txs";
+const char* const LMDB_OUTPUT_INDICES = "output_indices";
+const char* const LMDB_OUTPUT_AMOUNTS = "output_amounts";
+const char* const LMDB_OUTPUT_KEYS = "output_keys";
+const char* const LMDB_OUTPUTS = "outputs";
+const char* const LMDB_OUTPUT_GINDICES = "output_gindices";
+const char* const LMDB_SPENT_KEYS = "spent_keys";
+
+inline void lmdb_db_open(MDB_txn* txn, const char* name, int flags, MDB_dbi& dbi, const std::string& error_string)
+{
+  if (mdb_dbi_open(txn, name, flags, &dbi))
+    throw0(cryptonote::DB_OPEN_FAILURE(error_string.c_str()));
+}
+
+}  // anonymous namespace
+
+namespace cryptonote
+{
+
+void BlockchainLMDB::add_block( const block& blk
+              , const size_t& block_size
+              , const difficulty_type& cumulative_difficulty
+              , const uint64_t& coins_generated
+              , const crypto::hash& blk_hash
+              )
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<crypto::hash> val_h(blk_hash);
+  MDB_val unused;
+  if (mdb_get(*m_write_txn, m_block_heights, &val_h, &unused) == 0)
+    throw1(BLOCK_EXISTS("Attempting to add block that's already in the db"));
+
+  if (m_height > 0)
+  {
+    MDB_val_copy<crypto::hash> parent_key(blk.prev_id);
+    MDB_val parent_h;
+    if (mdb_get(*m_write_txn, m_block_heights, &parent_key, &parent_h))
+    {
+      LOG_PRINT_L3("m_height: " << m_height);
+      LOG_PRINT_L3("parent_key: " << blk.prev_id);
+      throw0(DB_ERROR("Failed to get top block hash to check for new block's parent"));
+    }
+    uint64_t parent_height = *(const uint64_t *)parent_h.mv_data;
+    if (parent_height != m_height - 1)
+      throw0(BLOCK_PARENT_DNE("Top block is not new block's parent"));
+  }
+
+  MDB_val_copy<uint64_t> key(m_height);
+
+  MDB_val_copy<blobdata> blob(block_to_blob(blk));
+  auto res = mdb_put(*m_write_txn, m_blocks, &key, &blob, 0);
+  if (res)
+    throw0(DB_ERROR(std::string("Failed to add block blob to db transaction: ").append(mdb_strerror(res)).c_str()));
+
+  MDB_val_copy<size_t> sz(block_size);
+  if (mdb_put(*m_write_txn, m_block_sizes, &key, &sz, 0))
+    throw0(DB_ERROR("Failed to add block size to db transaction"));
+
+  MDB_val_copy<uint64_t> ts(blk.timestamp);
+  if (mdb_put(*m_write_txn, m_block_timestamps, &key, &ts, 0))
+    throw0(DB_ERROR("Failed to add block timestamp to db transaction"));
+
+  MDB_val_copy<difficulty_type> diff(cumulative_difficulty);
+  if (mdb_put(*m_write_txn, m_block_diffs, &key, &diff, 0))
+    throw0(DB_ERROR("Failed to add block cumulative difficulty to db transaction"));
+
+  MDB_val_copy<uint64_t> coinsgen(coins_generated);
+  if (mdb_put(*m_write_txn, m_block_coins, &key, &coinsgen, 0))
+    throw0(DB_ERROR("Failed to add block total generated coins to db transaction"));
+
+  if (mdb_put(*m_write_txn, m_block_heights, &val_h, &key, 0))
+    throw0(DB_ERROR("Failed to add block height by hash to db transaction"));
+
+  if (mdb_put(*m_write_txn, m_block_hashes, &key, &val_h, 0))
+    throw0(DB_ERROR("Failed to add block hash to db transaction"));
+
+}
+
+void BlockchainLMDB::remove_block()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  if (m_height == 0)
+    throw0(BLOCK_DNE ("Attempting to remove block from an empty blockchain"));
+
+  MDB_val_copy<uint64_t> k(m_height - 1);
+  MDB_val h;
+  if (mdb_get(*m_write_txn, m_block_hashes, &k, &h))
+      throw1(BLOCK_DNE("Attempting to remove block that's not in the db"));
+
+  if (mdb_del(*m_write_txn, m_blocks, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_sizes, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block size to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_diffs, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block cumulative difficulty to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_coins, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block total generated coins to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_timestamps, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block timestamp to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_heights, &h, NULL))
+      throw1(DB_ERROR("Failed to add removal of block height by hash to db transaction"));
+
+  if (mdb_del(*m_write_txn, m_block_hashes, &k, NULL))
+      throw1(DB_ERROR("Failed to add removal of block hash to db transaction"));
+}
+
+void BlockchainLMDB::add_transaction_data(const crypto::hash& blk_hash, const transaction& tx, const crypto::hash& tx_hash)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<crypto::hash> val_h(tx_hash);
+  MDB_val unused;
+  if (mdb_get(*m_write_txn, m_txs, &val_h, &unused) == 0)
+      throw1(TX_EXISTS("Attempting to add transaction that's already in the db"));
+
+  MDB_val_copy<blobdata> blob(tx_to_blob(tx));
+  if (mdb_put(*m_write_txn, m_txs, &val_h, &blob, 0))
+    throw0(DB_ERROR("Failed to add tx blob to db transaction"));
+
+  MDB_val_copy<uint64_t> height(m_height);
+  if (mdb_put(*m_write_txn, m_tx_heights, &val_h, &height, 0))
+    throw0(DB_ERROR("Failed to add tx block height to db transaction"));
+
+  MDB_val_copy<uint64_t> unlock_time(tx.unlock_time);
+  if (mdb_put(*m_write_txn, m_tx_unlocks, &val_h, &unlock_time, 0))
+    throw0(DB_ERROR("Failed to add tx unlock time to db transaction"));
+}
+
+void BlockchainLMDB::remove_transaction_data(const crypto::hash& tx_hash, const transaction& tx)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<crypto::hash> val_h(tx_hash);
+  MDB_val unused;
+  if (mdb_get(*m_write_txn, m_txs, &val_h, &unused))
+      throw1(TX_DNE("Attempting to remove transaction that isn't in the db"));
+
+  if (mdb_del(*m_write_txn, m_txs, &val_h, NULL))
+      throw1(DB_ERROR("Failed to add removal of tx to db transaction"));
+  if (mdb_del(*m_write_txn, m_tx_unlocks, &val_h, NULL))
+      throw1(DB_ERROR("Failed to add removal of tx unlock time to db transaction"));
+  if (mdb_del(*m_write_txn, m_tx_heights, &val_h, NULL))
+      throw1(DB_ERROR("Failed to add removal of tx block height to db transaction"));
+
+  remove_tx_outputs(tx_hash, tx);
+
+  if (mdb_del(*m_write_txn, m_tx_outputs, &val_h, NULL))
+      throw1(DB_ERROR("Failed to add removal of tx outputs to db transaction"));
+
+}
+
+void BlockchainLMDB::add_output(const crypto::hash& tx_hash, const tx_out& tx_output, const uint64_t& local_index)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<uint64_t> k(m_num_outputs);
+  MDB_val_copy<crypto::hash> v(tx_hash);
+
+  if (mdb_put(*m_write_txn, m_output_txs, &k, &v, 0))
+    throw0(DB_ERROR("Failed to add output tx hash to db transaction"));
+  if (mdb_put(*m_write_txn, m_tx_outputs, &v, &k, 0))
+    throw0(DB_ERROR("Failed to add tx output index to db transaction"));
+
+  MDB_val_copy<uint64_t> val_local_index(local_index);
+  if (mdb_put(*m_write_txn, m_output_indices, &k, &val_local_index, 0))
+    throw0(DB_ERROR("Failed to add tx output index to db transaction"));
+
+  MDB_val_copy<uint64_t> val_amount(tx_output.amount);
+  if (auto result = mdb_put(*m_write_txn, m_output_amounts, &val_amount, &k, 0))
+    throw0(DB_ERROR(std::string("Failed to add output amount to db transaction").append(mdb_strerror(result)).c_str()));
+
+  if (tx_output.target.type() == typeid(txout_to_key))
+  {
+    MDB_val_copy<crypto::public_key> val_pubkey(boost::get<txout_to_key>(tx_output.target).key);
+    if (mdb_put(*m_write_txn, m_output_keys, &k, &val_pubkey, 0))
+      throw0(DB_ERROR("Failed to add output pubkey to db transaction"));
+  }
+
+
+/****** Uncomment if ever outputs actually need to be stored in this manner
+ *
+  blobdata b = output_to_blob(tx_output);
+
+  v.mv_size = b.size();
+  v.mv_data = &b;
+  if (mdb_put(*m_write_txn, m_outputs, &k, &v, 0))
+    throw0(DB_ERROR("Failed to add output to db transaction"));
+  if (mdb_put(*m_write_txn, m_output_gindices, &v, &k, 0))
+    throw0(DB_ERROR("Failed to add output global index to db transaction"));
+************************************************************************/
+
+  m_num_outputs++;
+}
+
+void BlockchainLMDB::remove_tx_outputs(const crypto::hash& tx_hash, const transaction& tx)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+
+  lmdb_cur cur(*m_write_txn, m_tx_outputs);
+
+  MDB_val_copy<crypto::hash> k(tx_hash);
+  MDB_val v;
+
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+  {
+    LOG_ERROR("Attempting to remove a tx's outputs, but none found.  Continuing, but...be wary, because that's weird.");
+  }
+  else if (result)
+  {
+    throw0(DB_ERROR("DB error attempting to get an output"));
+  }
+  else
+  {
+    size_t num_elems = 0;
+    mdb_cursor_count(cur, &num_elems);
+
+    mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+    for (uint64_t i = 0; i < num_elems; ++i)
+    {
+      const tx_out tx_output = tx.vout[i];
+      remove_output(*(const uint64_t*)v.mv_data, tx_output.amount);
+      if (i < num_elems - 1)
+      {
+        mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+      }
+    }
+  }
+
+  cur.close();
+}
+
+// TODO: probably remove this function
+void BlockchainLMDB::remove_output(const tx_out& tx_output)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__ << " (unused version - does nothing)");
+  return;
+}
+
+void BlockchainLMDB::remove_output(const uint64_t& out_index, const uint64_t amount)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<uint64_t> k(out_index);
+
+/****** Uncomment if ever outputs actually need to be stored in this manner
+  blobdata b;
+  t_serializable_object_to_blob(tx_output, b);
+  k.mv_size = b.size();
+  k.mv_data = &b;
+
+  if (mdb_get(*m_write_txn, m_output_gindices, &k, &v))
+      throw1(OUTPUT_DNE("Attempting to remove output that does not exist"));
+
+  uint64_t gindex = *(uint64_t*)v.mv_data;
+
+  auto result = mdb_del(*m_write_txn, m_output_gindices, &k, NULL);
+  if (result != 0 && result != MDB_NOTFOUND)
+      throw1(DB_ERROR("Error adding removal of output global index to db transaction"));
+
+  result = mdb_del(*m_write_txn, m_outputs, &v, NULL);
+  if (result != 0 && result != MDB_NOTFOUND)
+      throw1(DB_ERROR("Error adding removal of output to db transaction"));
+*********************************************************************/
+
+  auto result = mdb_del(*m_write_txn, m_output_indices, &k, NULL);
+  if (result == MDB_NOTFOUND)
+  {
+    LOG_PRINT_L0("Unexpected: global output index not found in m_output_indices");
+  }
+  else if (result)
+  {
+    throw1(DB_ERROR("Error adding removal of output tx index to db transaction"));
+  }
+
+  result = mdb_del(*m_write_txn, m_output_txs, &k, NULL);
+  // if (result != 0 && result != MDB_NOTFOUND)
+  //    throw1(DB_ERROR("Error adding removal of output tx hash to db transaction"));
+  if (result == MDB_NOTFOUND)
+  {
+    LOG_PRINT_L0("Unexpected: global output index not found in m_output_txs");
+  }
+  else if (result)
+  {
+    throw1(DB_ERROR("Error adding removal of output tx hash to db transaction"));
+  }
+
+  result = mdb_del(*m_write_txn, m_output_keys, &k, NULL);
+  if (result == MDB_NOTFOUND)
+  {
+      LOG_PRINT_L0("Unexpected: global output index not found in m_output_keys");
+  }
+  else if (result)
+    throw1(DB_ERROR("Error adding removal of output pubkey to db transaction"));
+
+  remove_amount_output_index(amount, out_index);
+
+  m_num_outputs--;
+}
+
+void BlockchainLMDB::remove_amount_output_index(const uint64_t amount, const uint64_t global_output_index)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  lmdb_cur cur(*m_write_txn, m_output_amounts);
+
+  MDB_val_copy<uint64_t> k(amount);
+  MDB_val v;
+
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but amount not found"));
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get an output"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+
+  mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+  uint64_t amount_output_index = 0;
+  uint64_t goi = 0;
+  bool found_index = false;
+  for (uint64_t i = 0; i < num_elems; ++i)
+  {
+    mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+    goi = *(const uint64_t *)v.mv_data;
+    if (goi == global_output_index)
+    {
+      amount_output_index = i;
+      found_index = true;
+      break;
+    }
+    mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+  }
+  if (found_index)
+  {
+    // found the amount output index
+    // now delete it
+    result = mdb_cursor_del(cur, 0);
+    if (result)
+      throw0(DB_ERROR(std::string("Error deleting amount output index ").append(boost::lexical_cast<std::string>(amount_output_index)).c_str()));
+  }
+  else
+  {
+    // not found
+    cur.close();
+    throw1(OUTPUT_DNE("Failed to find amount output index"));
+  }
+  cur.close();
+}
+
+void BlockchainLMDB::add_spent_key(const crypto::key_image& k_image)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<crypto::key_image> val_key(k_image);
+  MDB_val unused;
+  if (mdb_get(*m_write_txn, m_spent_keys, &val_key, &unused) == 0)
+      throw1(KEY_IMAGE_EXISTS("Attempting to add spent key image that's already in the db"));
+
+  char anything = '\0';
+  unused.mv_size = sizeof(char);
+  unused.mv_data = &anything;
+  if (auto result = mdb_put(*m_write_txn, m_spent_keys, &val_key, &unused, 0))
+    throw1(DB_ERROR(std::string("Error adding spent key image to db transaction: ").append(mdb_strerror(result)).c_str()));
+}
+
+void BlockchainLMDB::remove_spent_key(const crypto::key_image& k_image)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  MDB_val_copy<crypto::key_image> k(k_image);
+  auto result = mdb_del(*m_write_txn, m_spent_keys, &k, NULL);
+  if (result != 0 && result != MDB_NOTFOUND)
+      throw1(DB_ERROR("Error adding removal of key image to db transaction"));
+}
+
+blobdata BlockchainLMDB::output_to_blob(const tx_out& output)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  blobdata b;
+  if (!t_serializable_object_to_blob(output, b))
+    throw1(DB_ERROR("Error serializing output to blob"));
+  return b;
+}
+
+tx_out BlockchainLMDB::output_from_blob(const blobdata& blob) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  std::stringstream ss;
+  ss << blob;
+  binary_archive<false> ba(ss);
+  tx_out o;
+
+  if (!(::serialization::serialize(ba, o)))
+    throw1(DB_ERROR("Error deserializing tx output blob"));
+
+  return o;
+}
+
+uint64_t BlockchainLMDB::get_output_global_index(const uint64_t& amount, const uint64_t& index) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  lmdb_cur cur(txn, m_output_amounts);
+
+  MDB_val_copy<uint64_t> k(amount);
+  MDB_val v;
+
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but amount not found"));
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get an output"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+  if (num_elems <= index)
+    throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but output not found"));
+
+  mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+  for (uint64_t i = 0; i < index; ++i)
+  {
+    mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+  }
+
+  mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+
+  uint64_t glob_index = *(const uint64_t*)v.mv_data;
+
+  cur.close();
+
+  txn.commit();
+
+  return glob_index;
+}
+
+void BlockchainLMDB::check_open() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (!m_open)
+    throw0(DB_ERROR("DB operation attempted on a not-open DB instance"));
+}
+
+BlockchainLMDB::~BlockchainLMDB()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+
+  // batch transaction shouldn't be active at this point. If it is, consider it aborted.
+  if (m_batch_active)
+    batch_abort();
+}
+
+BlockchainLMDB::BlockchainLMDB(bool batch_transactions)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  // initialize folder to something "safe" just in case
+  // someone accidentally misuses this class...
+  m_folder = "thishsouldnotexistbecauseitisgibberish";
+  m_open = false;
+
+  m_batch_transactions = batch_transactions;
+  m_write_txn = nullptr;
+  m_batch_active = false;
+  m_height = 0;
+}
+
+void BlockchainLMDB::open(const std::string& filename)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+
+  if (m_open)
+    throw0(DB_OPEN_FAILURE("Attempted to open db, but it's already open"));
+
+  boost::filesystem::path direc(filename);
+  if (boost::filesystem::exists(direc))
+  {
+    if (!boost::filesystem::is_directory(direc))
+      throw0(DB_OPEN_FAILURE("LMDB needs a directory path, but a file was passed"));
+  }
+  else
+  {
+    if (!boost::filesystem::create_directory(direc))
+      throw0(DB_OPEN_FAILURE(std::string("Failed to create directory ").append(filename).c_str()));
+  }
+
+  // check for existing LMDB files in base directory
+  boost::filesystem::path old_files = direc.parent_path();
+  if (boost::filesystem::exists(old_files / "data.mdb") ||
+      boost::filesystem::exists(old_files / "lock.mdb"))
+  {
+    LOG_PRINT_L0("Found existing LMDB files in " << old_files.c_str());
+    LOG_PRINT_L0("Move data.mdb and/or lock.mdb to " << filename << ", or delete them, and then restart");
+    throw DB_ERROR("Database could not be opened");
+  }
+
+  m_folder = filename;
+
+  // set up lmdb environment
+  if (mdb_env_create(&m_env))
+    throw0(DB_ERROR("Failed to create lmdb environment"));
+  if (mdb_env_set_maxdbs(m_env, 20))
+    throw0(DB_ERROR("Failed to set max number of dbs"));
+
+  size_t mapsize = 1LL << 34;
+  if (auto result = mdb_env_set_mapsize(m_env, mapsize))
+    throw0(DB_ERROR(std::string("Failed to set max memory map size: ").append(mdb_strerror(result)).c_str()));
+  if (auto result = mdb_env_open(m_env, filename.c_str(), 0, 0644))
+    throw0(DB_ERROR(std::string("Failed to open lmdb environment: ").append(mdb_strerror(result)).c_str()));
+
+  // get a read/write MDB_txn
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, 0, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  // open necessary databases, and set properties as needed
+  // uses macros to avoid having to change things too many places
+  lmdb_db_open(txn, LMDB_BLOCKS, MDB_INTEGERKEY | MDB_CREATE, m_blocks, "Failed to open db handle for m_blocks");
+
+  lmdb_db_open(txn, LMDB_BLOCK_TIMESTAMPS, MDB_INTEGERKEY | MDB_CREATE, m_block_timestamps, "Failed to open db handle for m_block_timestamps");
+  lmdb_db_open(txn, LMDB_BLOCK_HEIGHTS, MDB_CREATE, m_block_heights, "Failed to open db handle for m_block_heights");
+  lmdb_db_open(txn, LMDB_BLOCK_HASHES, MDB_INTEGERKEY | MDB_CREATE, m_block_hashes, "Failed to open db handle for m_block_hashes");
+  lmdb_db_open(txn, LMDB_BLOCK_SIZES, MDB_INTEGERKEY | MDB_CREATE, m_block_sizes, "Failed to open db handle for m_block_sizes");
+  lmdb_db_open(txn, LMDB_BLOCK_DIFFS, MDB_INTEGERKEY | MDB_CREATE, m_block_diffs, "Failed to open db handle for m_block_diffs");
+  lmdb_db_open(txn, LMDB_BLOCK_COINS, MDB_INTEGERKEY | MDB_CREATE, m_block_coins, "Failed to open db handle for m_block_coins");
+
+  lmdb_db_open(txn, LMDB_TXS, MDB_CREATE, m_txs, "Failed to open db handle for m_txs");
+  lmdb_db_open(txn, LMDB_TX_UNLOCKS, MDB_CREATE, m_tx_unlocks, "Failed to open db handle for m_tx_unlocks");
+  lmdb_db_open(txn, LMDB_TX_HEIGHTS, MDB_CREATE, m_tx_heights, "Failed to open db handle for m_tx_heights");
+  lmdb_db_open(txn, LMDB_TX_OUTPUTS, MDB_DUPSORT | MDB_CREATE, m_tx_outputs, "Failed to open db handle for m_tx_outputs");
+
+  lmdb_db_open(txn, LMDB_OUTPUT_TXS, MDB_INTEGERKEY | MDB_CREATE, m_output_txs, "Failed to open db handle for m_output_txs");
+  lmdb_db_open(txn, LMDB_OUTPUT_INDICES, MDB_INTEGERKEY | MDB_CREATE, m_output_indices, "Failed to open db handle for m_output_indices");
+  lmdb_db_open(txn, LMDB_OUTPUT_AMOUNTS, MDB_INTEGERKEY | MDB_DUPSORT | MDB_CREATE, m_output_amounts, "Failed to open db handle for m_output_amounts");
+  lmdb_db_open(txn, LMDB_OUTPUT_KEYS, MDB_INTEGERKEY | MDB_CREATE, m_output_keys, "Failed to open db handle for m_output_keys");
+
+/*************** not used, but kept for posterity
+  lmdb_db_open(txn, LMDB_OUTPUTS, MDB_INTEGERKEY | MDB_CREATE, m_outputs, "Failed to open db handle for m_outputs");
+  lmdb_db_open(txn, LMDB_OUTPUT_GINDICES, MDB_CREATE, m_output_gindices, "Failed to open db handle for m_output_gindices");
+*************************************************/
+
+  lmdb_db_open(txn, LMDB_SPENT_KEYS, MDB_CREATE, m_spent_keys, "Failed to open db handle for m_spent_keys");
+
+  mdb_set_dupsort(txn, m_output_amounts, compare_uint64);
+  mdb_set_dupsort(txn, m_tx_outputs, compare_uint64);
+
+  // get and keep current height
+  MDB_stat db_stats;
+  if (mdb_stat(txn, m_blocks, &db_stats))
+    throw0(DB_ERROR("Failed to query m_blocks"));
+  LOG_PRINT_L2("Setting m_height to: " << db_stats.ms_entries);
+  m_height = db_stats.ms_entries;
+
+  // get and keep current number of outputs
+  if (mdb_stat(txn, m_output_indices, &db_stats))
+    throw0(DB_ERROR("Failed to query m_output_indices"));
+  m_num_outputs = db_stats.ms_entries;
+
+  // commit the transaction
+  txn.commit();
+
+  m_open = true;
+  // from here, init should be finished
+}
+
+// unused for now, create will happen on open if doesn't exist
+void BlockchainLMDB::create(const std::string& filename)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  throw DB_CREATE_FAILURE("create() is not implemented for this BlockchainDB, open() will create files if needed.");
+}
+
+void BlockchainLMDB::close()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (m_batch_active)
+  {
+    LOG_PRINT_L3("close() first calling batch_abort() due to active batch transaction");
+    batch_abort();
+  }
+  this->sync();
+
+  // FIXME: not yet thread safe!!!  Use with care.
+  mdb_env_close(m_env);
+}
+
+void BlockchainLMDB::sync()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  // Does nothing unless LMDB environment was opened with MDB_NOSYNC or in part
+  // MDB_NOMETASYNC. Force flush to be synchronous.
+  if (auto result = mdb_env_sync(m_env, true))
+  {
+    throw0(DB_ERROR(std::string("Failed to sync database").append(mdb_strerror(result)).c_str()));
+  }
+}
+
+void BlockchainLMDB::reset()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  // TODO: this
+}
+
+std::vector<std::string> BlockchainLMDB::get_filenames() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  std::vector<std::string> filenames;
+
+  boost::filesystem::path datafile(m_folder);
+  datafile /= "data.mdb";
+  boost::filesystem::path lockfile(m_folder);
+  lockfile /= "lock.mdb";
+
+  filenames.push_back(datafile.string());
+  filenames.push_back(lockfile.string());
+
+  return filenames;
+}
+
+// TODO: this?
+bool BlockchainLMDB::lock()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  return false;
+}
+
+// TODO: this?
+void BlockchainLMDB::unlock()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+}
+
+bool BlockchainLMDB::block_exists(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+  auto get_result = mdb_get(txn, m_block_heights, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    txn.commit();
+    LOG_PRINT_L3("Block with hash " << epee::string_tools::pod_to_hex(h) << " not found in db");
+    return false;
+  }
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch block index from hash"));
+
+  txn.commit();
+  return true;
+}
+
+block BlockchainLMDB::get_block(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  return get_block_from_height(get_block_height(h));
+}
+
+uint64_t BlockchainLMDB::get_block_height(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+  auto get_result = mdb_get(txn, m_block_heights, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+    throw1(BLOCK_DNE("Attempted to retrieve non-existent block height"));
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a block height from the db"));
+
+  txn.commit();
+  return *(const uint64_t*)result.mv_data;
+}
+
+block_header BlockchainLMDB::get_block_header(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  // block_header object is automatically cast from block object
+  return get_block(h);
+}
+
+block BlockchainLMDB::get_block_from_height(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(txn, m_blocks, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(DB_ERROR(std::string("Attempt to get block from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- block not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a block from the db"));
+
+  txn.commit();
+
+  blobdata bd;
+  bd.assign(reinterpret_cast<char*>(result.mv_data), result.mv_size);
+
+  block b;
+  if (!parse_and_validate_block_from_blob(bd, b))
+    throw0(DB_ERROR("Failed to parse block from blob retrieved from the db"));
+
+  return b;
+}
+
+uint64_t BlockchainLMDB::get_block_timestamp(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_block_timestamps, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(DB_ERROR(std::string("Attempt to get timestamp from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- timestamp not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a timestamp from the db"));
+
+  if (! m_batch_active)
+    txn.commit();
+  return *(const uint64_t*)result.mv_data;
+}
+
+uint64_t BlockchainLMDB::get_top_block_timestamp() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  // if no blocks, return 0
+  if (m_height == 0)
+  {
+    return 0;
+  }
+
+  return get_block_timestamp(m_height - 1);
+}
+
+size_t BlockchainLMDB::get_block_size(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_block_sizes, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(DB_ERROR(std::string("Attempt to get block size from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- block size not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a block size from the db"));
+
+  if (! m_batch_active)
+    txn.commit();
+  return *(const size_t*)result.mv_data;
+}
+
+difficulty_type BlockchainLMDB::get_block_cumulative_difficulty(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__ << "  height: " << height);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_block_diffs, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(DB_ERROR(std::string("Attempt to get cumulative difficulty from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- difficulty not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a cumulative difficulty from the db"));
+
+  if (! m_batch_active)
+    txn.commit();
+  return *(difficulty_type*)result.mv_data;
+}
+
+difficulty_type BlockchainLMDB::get_block_difficulty(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  difficulty_type diff1 = 0;
+  difficulty_type diff2 = 0;
+
+  diff1 = get_block_cumulative_difficulty(height);
+  if (height != 0)
+  {
+    diff2 = get_block_cumulative_difficulty(height - 1);
+  }
+
+  return diff1 - diff2;
+}
+
+uint64_t BlockchainLMDB::get_block_already_generated_coins(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_block_coins, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(DB_ERROR(std::string("Attempt to get generated coins from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- block size not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve a total generated coins from the db"));
+
+  if (! m_batch_active)
+    txn.commit();
+  return *(const uint64_t*)result.mv_data;
+}
+
+crypto::hash BlockchainLMDB::get_block_hash_from_height(const uint64_t& height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<uint64_t> key(height);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_block_hashes, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw0(BLOCK_DNE(std::string("Attempt to get hash from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- hash not in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR(std::string("Error attempting to retrieve a block hash from the db: ").
+          append(mdb_strerror(get_result)).c_str()));
+
+  if (! m_batch_active)
+    txn.commit();
+  return *(crypto::hash*)result.mv_data;
+}
+
+std::vector<block> BlockchainLMDB::get_blocks_range(const uint64_t& h1, const uint64_t& h2) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  std::vector<block> v;
+
+  for (uint64_t height = h1; height <= h2; ++height)
+  {
+    v.push_back(get_block_from_height(height));
+  }
+
+  return v;
+}
+
+std::vector<crypto::hash> BlockchainLMDB::get_hashes_range(const uint64_t& h1, const uint64_t& h2) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  std::vector<crypto::hash> v;
+
+  for (uint64_t height = h1; height <= h2; ++height)
+  {
+    v.push_back(get_block_hash_from_height(height));
+  }
+
+  return v;
+}
+
+crypto::hash BlockchainLMDB::top_block_hash() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  if (m_height != 0)
+  {
+    return get_block_hash_from_height(m_height - 1);
+  }
+
+  return null_hash;
+}
+
+block BlockchainLMDB::get_top_block() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  if (m_height != 0)
+  {
+    return get_block_from_height(m_height - 1);
+  }
+
+  block b;
+  return b;
+}
+
+uint64_t BlockchainLMDB::height() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  return m_height;
+}
+
+bool BlockchainLMDB::tx_exists(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+
+  TIME_MEASURE_START(time1);
+  auto get_result = mdb_get(*txn_ptr, m_txs, &key, &result);
+  TIME_MEASURE_FINISH(time1);
+  time_tx_exists += time1;
+  if (get_result == MDB_NOTFOUND)
+  {
+    if (! m_batch_active)
+      txn.commit();
+    LOG_PRINT_L1("transaction with hash " << epee::string_tools::pod_to_hex(h) << " not found in db");
+    return false;
+  }
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch transaction from hash"));
+
+  return true;
+}
+
+uint64_t BlockchainLMDB::get_tx_unlock_time(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+  auto get_result = mdb_get(txn, m_tx_unlocks, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+    throw1(TX_DNE(std::string("tx unlock time with hash ").append(epee::string_tools::pod_to_hex(h)).append(" not found in db").c_str()));
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch tx unlock time from hash"));
+
+  return *(const uint64_t*)result.mv_data;
+}
+
+transaction BlockchainLMDB::get_tx(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_txs, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+    throw1(TX_DNE(std::string("tx with hash ").append(epee::string_tools::pod_to_hex(h)).append(" not found in db").c_str()));
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch tx from hash"));
+
+  blobdata bd;
+  bd.assign(reinterpret_cast<char*>(result.mv_data), result.mv_size);
+
+  transaction tx;
+  if (!parse_and_validate_tx_from_blob(bd, tx))
+    throw0(DB_ERROR("Failed to parse tx from blob retrieved from the db"));
+  if (! m_batch_active)
+    txn.commit();
+
+  return tx;
+}
+
+uint64_t BlockchainLMDB::get_tx_count() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_stat db_stats;
+  if (mdb_stat(txn, m_txs, &db_stats))
+    throw0(DB_ERROR("Failed to query m_txs"));
+
+  txn.commit();
+
+  return db_stats.ms_entries;
+}
+
+std::vector<transaction> BlockchainLMDB::get_tx_list(const std::vector<crypto::hash>& hlist) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  std::vector<transaction> v;
+
+  for (auto& h : hlist)
+  {
+    v.push_back(get_tx(h));
+  }
+
+  return v;
+}
+
+uint64_t BlockchainLMDB::get_tx_block_height(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  // If m_batch_active is set, a batch transaction exists beyond this class,
+  // such as a batch import with verification enabled, or possibly (later) a
+  // batch network sync.
+  //
+  // A regular network sync without batching would be expected to open a new
+  // read transaction here, as validation is done prior to the write for block
+  // and tx data.
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+
+  MDB_val_copy<crypto::hash> key(h);
+  MDB_val result;
+  auto get_result = mdb_get(*txn_ptr, m_tx_heights, &key, &result);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw1(TX_DNE(std::string("tx height with hash ").append(epee::string_tools::pod_to_hex(h)).append(" not found in db").c_str()));
+  }
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch tx height from hash"));
+
+  if (! m_batch_active)
+    txn.commit();
+
+  return *(const uint64_t*)result.mv_data;
+}
+
+//FIXME: make sure the random method used here is appropriate
+uint64_t BlockchainLMDB::get_random_output(const uint64_t& amount) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  uint64_t num_outputs = get_num_outputs(amount);
+  if (num_outputs == 0)
+    throw1(OUTPUT_DNE("Attempting to get a random output for an amount, but none exist"));
+
+  return crypto::rand<uint64_t>() % num_outputs;
+}
+
+uint64_t BlockchainLMDB::get_num_outputs(const uint64_t& amount) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  lmdb_cur cur(txn, m_output_amounts);
+
+  MDB_val_copy<uint64_t> k(amount);
+  MDB_val v;
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+  {
+    return 0;
+  }
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get number of outputs of an amount"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+
+  txn.commit();
+
+  return num_elems;
+}
+
+crypto::public_key BlockchainLMDB::get_output_key(const uint64_t& amount, const uint64_t& index) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  uint64_t glob_index = get_output_global_index(amount, index);
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<uint64_t> k(glob_index);
+  MDB_val v;
+  auto get_result = mdb_get(txn, m_output_keys, &k, &v);
+  if (get_result == MDB_NOTFOUND)
+    throw0(DB_ERROR("Attempting to get output pubkey by global index, but key does not exist"));
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve an output pubkey from the db"));
+
+  return *(crypto::public_key*)v.mv_data;
+}
+
+tx_out BlockchainLMDB::get_output(const crypto::hash& h, const uint64_t& index) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  lmdb_cur cur(txn, m_tx_outputs);
+
+  MDB_val_copy<crypto::hash> k(h);
+  MDB_val v;
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("Attempting to get an output by tx hash and tx index, but output not found"));
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get an output"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+  if (num_elems <= index)
+    throw1(OUTPUT_DNE("Attempting to get an output by tx hash and tx index, but output not found"));
+
+  mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+  for (uint64_t i = 0; i < index; ++i)
+  {
+    mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+  }
+
+  mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+
+  blobdata b;
+  b = *(blobdata*)v.mv_data;
+
+  cur.close();
+  txn.commit();
+
+  return output_from_blob(b);
+}
+
+// As this is not used, its return is now a blank output.
+// This will save on space in the db.
+tx_out BlockchainLMDB::get_output(const uint64_t& index) const
+{
+  return tx_out();
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<uint64_t> k(index);
+  MDB_val v;
+  auto get_result = mdb_get(txn, m_outputs, &k, &v);
+  if (get_result == MDB_NOTFOUND)
+  {
+    throw OUTPUT_DNE("Attempting to get output by global index, but output does not exist");
+  }
+  else if (get_result)
+    throw0(DB_ERROR("Error attempting to retrieve an output from the db"));
+
+  blobdata b = *(blobdata*)v.mv_data;
+
+  return output_from_blob(b);
+}
+
+tx_out_index BlockchainLMDB::get_output_tx_and_index_from_global(const uint64_t& index) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+  MDB_val_copy<uint64_t> k(index);
+  MDB_val v;
+
+  auto get_result = mdb_get(*txn_ptr, m_output_txs, &k, &v);
+  if (get_result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("output with given index not in db"));
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch output tx hash"));
+
+  crypto::hash tx_hash = *(crypto::hash*)v.mv_data;
+
+  get_result = mdb_get(*txn_ptr, m_output_indices, &k, &v);
+  if (get_result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("output with given index not in db"));
+  else if (get_result)
+    throw0(DB_ERROR("DB error attempting to fetch output tx index"));
+  if (! m_batch_active)
+    txn.commit();
+
+  return tx_out_index(tx_hash, *(const uint64_t *)v.mv_data);
+}
+
+tx_out_index BlockchainLMDB::get_output_tx_and_index(const uint64_t& amount, const uint64_t& index) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+  }
+  lmdb_cur cur(*txn_ptr, m_output_amounts);
+
+  MDB_val_copy<uint64_t> k(amount);
+  MDB_val v;
+
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but amount not found"));
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get an output"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+  if (num_elems <= index)
+    throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but output not found"));
+
+  mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+  for (uint64_t i = 0; i < index; ++i)
+  {
+    mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+  }
+
+  mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+
+  uint64_t glob_index = *(const uint64_t*)v.mv_data;
+
+  cur.close();
+
+  if (! m_batch_active)
+    txn.commit();
+
+  return get_output_tx_and_index_from_global(glob_index);
+}
+
+std::vector<uint64_t> BlockchainLMDB::get_tx_output_indices(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  std::vector<uint64_t> index_vec;
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  lmdb_cur cur(txn, m_tx_outputs);
+
+  MDB_val_copy<crypto::hash> k(h);
+  MDB_val v;
+  auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    throw1(OUTPUT_DNE("Attempting to get an output by tx hash and tx index, but output not found"));
+  else if (result)
+    throw0(DB_ERROR("DB error attempting to get an output"));
+
+  size_t num_elems = 0;
+  mdb_cursor_count(cur, &num_elems);
+
+  mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+  for (uint64_t i = 0; i < num_elems; ++i)
+  {
+    mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+    index_vec.push_back(*(const uint64_t *)v.mv_data);
+    mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+  }
+
+  cur.close();
+  txn.commit();
+
+  return index_vec;
+}
+
+std::vector<uint64_t> BlockchainLMDB::get_tx_amount_output_indices(const crypto::hash& h) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  std::vector<uint64_t> index_vec;
+  std::vector<uint64_t> index_vec2;
+
+  // get the transaction's global output indices first
+  index_vec = get_tx_output_indices(h);
+  // these are next used to obtain the amount output indices
+
+  transaction tx = get_tx(h);
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  uint64_t i = 0;
+  uint64_t global_index;
+  BOOST_FOREACH(const auto& vout, tx.vout)
+  {
+    uint64_t amount =  vout.amount;
+
+    global_index = index_vec[i];
+
+    lmdb_cur cur(txn, m_output_amounts);
+
+    MDB_val_copy<uint64_t> k(amount);
+    MDB_val v;
+
+    auto result = mdb_cursor_get(cur, &k, &v, MDB_SET);
+    if (result == MDB_NOTFOUND)
+      throw1(OUTPUT_DNE("Attempting to get an output index by amount and amount index, but amount not found"));
+    else if (result)
+      throw0(DB_ERROR("DB error attempting to get an output"));
+
+    size_t num_elems = 0;
+    mdb_cursor_count(cur, &num_elems);
+
+    mdb_cursor_get(cur, &k, &v, MDB_FIRST_DUP);
+
+    uint64_t amount_output_index = 0;
+    uint64_t output_index = 0;
+    bool found_index = false;
+    for (uint64_t j = 0; j < num_elems; ++j)
+    {
+      mdb_cursor_get(cur, &k, &v, MDB_GET_CURRENT);
+      output_index = *(const uint64_t *)v.mv_data;
+      if (output_index == global_index)
+      {
+        amount_output_index = j;
+        found_index = true;
+        break;
+      }
+      mdb_cursor_get(cur, &k, &v, MDB_NEXT_DUP);
+    }
+    if (found_index)
+    {
+      index_vec2.push_back(amount_output_index);
+    }
+    else
+    {
+      // not found
+      cur.close();
+      txn.commit();
+      throw1(OUTPUT_DNE("specified output not found in db"));
+    }
+
+    cur.close();
+    ++i;
+  }
+
+  txn.commit();
+
+  return index_vec2;
+}
+
+
+
+bool BlockchainLMDB::has_key_image(const crypto::key_image& img) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+
+  MDB_val_copy<crypto::key_image> val_key(img);
+  MDB_val unused;
+  if (mdb_get(txn, m_spent_keys, &val_key, &unused) == 0)
+  {
+    txn.commit();
+    return true;
+  }
+
+  txn.commit();
+  return false;
+}
+
+void BlockchainLMDB::batch_start()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (! m_batch_transactions)
+    throw0(DB_ERROR("batch transactions not enabled"));
+  if (m_batch_active)
+    throw0(DB_ERROR("batch transaction already in progress"));
+  if (m_write_txn)
+    throw0(DB_ERROR("batch transaction attempted, but m_write_txn already in use"));
+  check_open();
+  // NOTE: need to make sure it's destroyed properly when done
+  if (mdb_txn_begin(m_env, NULL, 0, m_write_batch_txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+  // indicates this transaction is for batch transactions, but not whether it's
+  // active
+  m_write_batch_txn.m_batch_txn = true;
+  m_write_txn = &m_write_batch_txn;
+  m_batch_active = true;
+  LOG_PRINT_L3("batch transaction: begin");
+}
+
+void BlockchainLMDB::batch_commit()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (! m_batch_transactions)
+    throw0(DB_ERROR("batch transactions not enabled"));
+  if (! m_batch_active)
+    throw0(DB_ERROR("batch transaction not in progress"));
+  check_open();
+  LOG_PRINT_L3("batch transaction: committing...");
+  TIME_MEASURE_START(time1);
+  m_write_txn->commit();
+  TIME_MEASURE_FINISH(time1);
+  time_commit1 += time1;
+  LOG_PRINT_L3("batch transaction: committed");
+
+  if (mdb_txn_begin(m_env, NULL, 0, m_write_batch_txn))
+    throw0(DB_ERROR("Failed to create a transaction for the db"));
+  if (! m_write_batch_txn.m_batch_txn)
+    throw0(DB_ERROR("m_write_batch_txn not marked as a batch transaction"));
+  m_write_txn = &m_write_batch_txn;
+}
+
+void BlockchainLMDB::batch_stop()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (! m_batch_transactions)
+    throw0(DB_ERROR("batch transactions not enabled"));
+  if (! m_batch_active)
+    throw0(DB_ERROR("batch transaction not in progress"));
+  check_open();
+  LOG_PRINT_L3("batch transaction: committing...");
+  TIME_MEASURE_START(time1);
+  m_write_txn->commit();
+  TIME_MEASURE_FINISH(time1);
+  time_commit1 += time1;
+  // for destruction of batch transaction
+  m_write_txn = nullptr;
+  m_batch_active = false;
+  LOG_PRINT_L3("batch transaction: end");
+}
+
+void BlockchainLMDB::batch_abort()
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  if (! m_batch_transactions)
+    throw0(DB_ERROR("batch transactions not enabled"));
+  if (! m_batch_active)
+    throw0(DB_ERROR("batch transaction not in progress"));
+  check_open();
+  // for destruction of batch transaction
+  m_write_txn = nullptr;
+  // explicitly call in case mdb_env_close() (BlockchainLMDB::close()) called before BlockchainLMDB destructor called.
+  m_write_batch_txn.abort();
+  m_batch_active = false;
+  LOG_PRINT_L3("batch transaction: aborted");
+}
+
+void BlockchainLMDB::set_batch_transactions(bool batch_transactions)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  m_batch_transactions = batch_transactions;
+  LOG_PRINT_L3("batch transactions " << (m_batch_transactions ? "enabled" : "disabled"));
+}
+
+uint64_t BlockchainLMDB::add_block( const block& blk
+                                  , const size_t& block_size
+                                  , const difficulty_type& cumulative_difficulty
+                                  , const uint64_t& coins_generated
+                                  , const std::vector<transaction>& txs
+                                  )
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (! m_batch_active)
+  {
+    if (mdb_txn_begin(m_env, NULL, 0, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    m_write_txn = &txn;
+  }
+
+  uint64_t num_outputs = m_num_outputs;
+  try
+  {
+    BlockchainDB::add_block(blk, block_size, cumulative_difficulty, coins_generated, txs);
+    if (! m_batch_active)
+    {
+      m_write_txn = NULL;
+
+      TIME_MEASURE_START(time1);
+      txn.commit();
+      TIME_MEASURE_FINISH(time1);
+      time_commit1 += time1;
+    }
+  }
+  catch (...)
+  {
+    m_num_outputs = num_outputs;
+    if (! m_batch_active)
+      m_write_txn = NULL;
+    throw;
+  }
+
+  return ++m_height;
+}
+
+void BlockchainLMDB::pop_block(block& blk, std::vector<transaction>& txs)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  txn_safe txn;
+  if (! m_batch_active)
+  {
+    if (mdb_txn_begin(m_env, NULL, 0, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    m_write_txn = &txn;
+  }
+
+  uint64_t num_outputs = m_num_outputs;
+  try
+  {
+    BlockchainDB::pop_block(blk, txs);
+    if (! m_batch_active)
+    {
+      m_write_txn = NULL;
+
+      txn.commit();
+    }
+  }
+  catch (...)
+  {
+    m_num_outputs = num_outputs;
+    m_write_txn = NULL;
+    throw;
+  }
+
+  --m_height;
+}
+
+}  // namespace cryptonote
diff --git a/src/blockchain_db/lmdb/db_lmdb.h b/src/blockchain_db/lmdb/db_lmdb.h
new file mode 100644
index 000000000..f6582fce4
--- /dev/null
+++ b/src/blockchain_db/lmdb/db_lmdb.h
@@ -0,0 +1,314 @@
+// Copyright (c) 2014, The Monero Project
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "blockchain_db/blockchain_db.h"
+#include "cryptonote_protocol/blobdatatype.h" // for type blobdata
+
+#include <lmdb.h>
+
+namespace cryptonote
+{
+
+struct txn_safe
+{
+  txn_safe() : m_txn(NULL) { }
+  ~txn_safe()
+  {
+    LOG_PRINT_L3("txn_safe: destructor");
+    if (m_txn != NULL)
+    {
+      if (m_batch_txn) // this is a batch txn and should have been handled before this point for safety
+      {
+        LOG_PRINT_L0("WARNING: txn_safe: m_txn is a batch txn and it's not NULL in destructor - calling mdb_txn_abort()");
+      }
+      else
+      {
+        // Example of when this occurs: a lookup fails, so a read-only txn is
+        // aborted through this destructor. However, successful read-only txns
+        // ideally should have been committed when done and not end up here.
+        //
+        // NOTE: not sure if this is ever reached for a non-batch write
+        // transaction, but it's probably not ideal if it did.
+        LOG_PRINT_L3("txn_safe: m_txn not NULL in destructor - calling mdb_txn_abort()");
+      }
+      mdb_txn_abort(m_txn);
+    }
+  }
+
+  void commit(std::string message = "")
+  {
+    if (message.size() == 0)
+    {
+      message = "Failed to commit a transaction to the db";
+    }
+
+    if (mdb_txn_commit(m_txn))
+    {
+      m_txn = NULL;
+      LOG_PRINT_L0(message);
+      throw DB_ERROR(message.c_str());
+    }
+    m_txn = NULL;
+  }
+
+  // This should only be needed for batch transaction which must be ensured to
+  // be aborted before mdb_env_close, not after. So we can't rely on
+  // BlockchainLMDB destructor to call txn_safe destructor, as that's too late
+  // to properly abort, since mdb_env_close would have been called earlier.
+  void abort()
+  {
+    LOG_PRINT_L3("txn_safe: abort()");
+    if(m_txn != NULL)
+    {
+      mdb_txn_abort(m_txn);
+      m_txn = NULL;
+    }
+    else
+    {
+      LOG_PRINT_L0("WARNING: txn_safe: abort() called, but m_txn is NULL");
+    }
+  }
+
+  operator MDB_txn*()
+  {
+    return m_txn;
+  }
+
+  operator MDB_txn**()
+  {
+    return &m_txn;
+  }
+
+  MDB_txn* m_txn;
+  bool m_batch_txn = false;
+};
+
+
+class BlockchainLMDB : public BlockchainDB
+{
+public:
+  BlockchainLMDB(bool batch_transactions=false);
+  ~BlockchainLMDB();
+
+  virtual void open(const std::string& filename);
+
+  virtual void create(const std::string& filename);
+
+  virtual void close();
+
+  virtual void sync();
+
+  virtual void reset();
+
+  virtual std::vector<std::string> get_filenames() const;
+
+  virtual bool lock();
+
+  virtual void unlock();
+
+  virtual bool block_exists(const crypto::hash& h) const;
+
+  virtual block get_block(const crypto::hash& h) const;
+
+  virtual uint64_t get_block_height(const crypto::hash& h) const;
+
+  virtual block_header get_block_header(const crypto::hash& h) const;
+
+  virtual block get_block_from_height(const uint64_t& height) const;
+
+  virtual uint64_t get_block_timestamp(const uint64_t& height) const;
+
+  virtual uint64_t get_top_block_timestamp() const;
+
+  virtual size_t get_block_size(const uint64_t& height) const;
+
+  virtual difficulty_type get_block_cumulative_difficulty(const uint64_t& height) const;
+
+  virtual difficulty_type get_block_difficulty(const uint64_t& height) const;
+
+  virtual uint64_t get_block_already_generated_coins(const uint64_t& height) const;
+
+  virtual crypto::hash get_block_hash_from_height(const uint64_t& height) const;
+
+  virtual std::vector<block> get_blocks_range(const uint64_t& h1, const uint64_t& h2) const;
+
+  virtual std::vector<crypto::hash> get_hashes_range(const uint64_t& h1, const uint64_t& h2) const;
+
+  virtual crypto::hash top_block_hash() const;
+
+  virtual block get_top_block() const;
+
+  virtual uint64_t height() const;
+
+  virtual bool tx_exists(const crypto::hash& h) const;
+
+  virtual uint64_t get_tx_unlock_time(const crypto::hash& h) const;
+
+  virtual transaction get_tx(const crypto::hash& h) const;
+
+  virtual uint64_t get_tx_count() const;
+
+  virtual std::vector<transaction> get_tx_list(const std::vector<crypto::hash>& hlist) const;
+
+  virtual uint64_t get_tx_block_height(const crypto::hash& h) const;
+
+  virtual uint64_t get_random_output(const uint64_t& amount) const;
+
+  virtual uint64_t get_num_outputs(const uint64_t& amount) const;
+
+  virtual crypto::public_key get_output_key(const uint64_t& amount, const uint64_t& index) const;
+
+  virtual tx_out get_output(const crypto::hash& h, const uint64_t& index) const;
+
+  /**
+   * @brief get an output from its global index
+   *
+   * @param index global index of the output desired
+   *
+   * @return the output associated with the index.
+   * Will throw OUTPUT_DNE if not output has that global index.
+   * Will throw DB_ERROR if there is a non-specific LMDB error in fetching
+   */
+  tx_out get_output(const uint64_t& index) const;
+
+  virtual tx_out_index get_output_tx_and_index_from_global(const uint64_t& index) const;
+
+  virtual tx_out_index get_output_tx_and_index(const uint64_t& amount, const uint64_t& index) const;
+
+  virtual std::vector<uint64_t> get_tx_output_indices(const crypto::hash& h) const;
+  virtual std::vector<uint64_t> get_tx_amount_output_indices(const crypto::hash& h) const;
+
+  virtual bool has_key_image(const crypto::key_image& img) const;
+
+  virtual uint64_t add_block( const block& blk
+                            , const size_t& block_size
+                            , const difficulty_type& cumulative_difficulty
+                            , const uint64_t& coins_generated
+                            , const std::vector<transaction>& txs
+                            );
+
+  virtual void set_batch_transactions(bool batch_transactions);
+  virtual void batch_start();
+  virtual void batch_commit();
+  virtual void batch_stop();
+  virtual void batch_abort();
+
+  virtual void pop_block(block& blk, std::vector<transaction>& txs);
+
+private:
+  virtual void add_block( const block& blk
+                , const size_t& block_size
+                , const difficulty_type& cumulative_difficulty
+                , const uint64_t& coins_generated
+                , const crypto::hash& block_hash
+                );
+
+  virtual void remove_block();
+
+  virtual void add_transaction_data(const crypto::hash& blk_hash, const transaction& tx, const crypto::hash& tx_hash);
+
+  virtual void remove_transaction_data(const crypto::hash& tx_hash, const transaction& tx);
+
+  virtual void add_output(const crypto::hash& tx_hash, const tx_out& tx_output, const uint64_t& local_index);
+
+  virtual void remove_output(const tx_out& tx_output);
+
+  void remove_tx_outputs(const crypto::hash& tx_hash, const transaction& tx);
+
+  void remove_output(const uint64_t& out_index, const uint64_t amount);
+  void remove_amount_output_index(const uint64_t amount, const uint64_t global_output_index);
+
+  virtual void add_spent_key(const crypto::key_image& k_image);
+
+  virtual void remove_spent_key(const crypto::key_image& k_image);
+
+  /**
+   * @brief convert a tx output to a blob for storage
+   *
+   * @param output the output to convert
+   *
+   * @return the resultant blob
+   */
+  blobdata output_to_blob(const tx_out& output);
+
+  /**
+   * @brief convert a tx output blob to a tx output
+   *
+   * @param blob the blob to convert
+   *
+   * @return the resultant tx output
+   */
+  tx_out output_from_blob(const blobdata& blob) const;
+
+  /**
+   * @brief get the global index of the index-th output of the given amount
+   *
+   * @param amount the output amount
+   * @param index the index into the set of outputs of that amount
+   *
+   * @return the global index of the desired output
+   */
+  uint64_t get_output_global_index(const uint64_t& amount, const uint64_t& index) const;
+
+  void check_open() const;
+
+  MDB_env* m_env;
+
+  MDB_dbi m_blocks;
+  MDB_dbi m_block_heights;
+  MDB_dbi m_block_hashes;
+  MDB_dbi m_block_timestamps;
+  MDB_dbi m_block_sizes;
+  MDB_dbi m_block_diffs;
+  MDB_dbi m_block_coins;
+
+  MDB_dbi m_txs;
+  MDB_dbi m_tx_unlocks;
+  MDB_dbi m_tx_heights;
+  MDB_dbi m_tx_outputs;
+
+  MDB_dbi m_output_txs;
+  MDB_dbi m_output_indices;
+  MDB_dbi m_output_gindices;
+  MDB_dbi m_output_amounts;
+  MDB_dbi m_output_keys;
+  MDB_dbi m_outputs;
+
+  MDB_dbi m_spent_keys;
+
+  bool m_open;
+  uint64_t m_height;
+  uint64_t m_num_outputs;
+  std::string m_folder;
+  txn_safe* m_write_txn; // may point to either a short-lived txn or a batch txn
+  txn_safe m_write_batch_txn; // persist batch txn outside of BlockchainLMDB
+
+  bool m_batch_transactions; // support for batch transactions
+  bool m_batch_active; // whether batch transaction is in progress
+};
+
+}  // namespace cryptonote