db_lmdb: always use a batch tx if possible

Also wrap that code in two prefix/suffix macros so they are
easier to use and not forget. Also add consts to returned data
casts where applicable.

1 files changed, 127 insertions, 290 deletions

diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index b941fe6b1..f76fee87a 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -29,6 +29,7 @@
 
 #include <boost/filesystem.hpp>
 #include <boost/format.hpp>
+#include <boost/current_function.hpp>
 #include <memory>  // std::unique_ptr
 #include <cstring>  // memcpy
 #include <random>
@@ -1232,28 +1233,45 @@ void BlockchainLMDB::unlock()
   check_open();
 }
 
+#define TXN_PREFIX(flags); \
+  mdb_txn_safe auto_txn; \
+  mdb_txn_safe* txn_ptr = &auto_txn; \
+  if (m_batch_active) \
+    txn_ptr = m_write_txn; \
+  else \
+  { \
+    if (auto mdb_res = mdb_txn_begin(m_env, NULL, flags, auto_txn)) \
+      throw0(DB_ERROR(lmdb_error(std::string("Failed to create a transaction for the db in ")+__FUNCTION__+": ", mdb_res).c_str())); \
+  } \
+
+#define TXN_PREFIX_RDONLY(); TXN_PREFIX(MDB_RDONLY);
+
+#define TXN_POSTFIX_SUCCESS() \
+  do { \
+    if (! m_batch_active) \
+      auto_txn.commit(); \
+  } while(0)
+
 bool BlockchainLMDB::block_exists(const crypto::hash& h) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
-  auto get_result = mdb_get(txn, m_block_heights, &key, &result);
+  auto get_result = mdb_get(*txn_ptr, m_block_heights, &key, &result);
   if (get_result == MDB_NOTFOUND)
   {
-    txn.commit();
+    TXN_POSTFIX_SUCCESS();
     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();
+  TXN_POSTFIX_SUCCESS();
   return true;
 }
 
@@ -1270,21 +1288,18 @@ uint64_t BlockchainLMDB::get_block_height(const crypto::hash& h) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
-  auto get_result = mdb_get(txn, m_block_heights, &key, &result);
+  auto get_result = mdb_get(*txn_ptr, 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"));
 
-  ret = *(const uint64_t *)result.mv_data;
-  txn.commit();
+  uint64_t ret = *(const uint64_t *)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1302,13 +1317,11 @@ block BlockchainLMDB::get_block_from_height(const uint64_t& height) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
-  auto get_result = mdb_get(txn, m_blocks, &key, &result);
+  auto get_result = mdb_get(*txn_ptr, m_blocks, &key, &result);
   if (get_result == MDB_NOTFOUND)
   {
     throw0(BLOCK_DNE(std::string("Attempt to get block from height ").append(boost::lexical_cast<std::string>(height)).append(" failed -- block not in db").c_str()));
@@ -1323,7 +1336,7 @@ block BlockchainLMDB::get_block_from_height(const uint64_t& height) const
   if (!parse_and_validate_block_from_blob(bd, b))
     throw0(DB_ERROR("Failed to parse block from blob retrieved from the db"));
 
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return b;
 }
@@ -1333,16 +1346,8 @@ uint64_t BlockchainLMDB::get_block_timestamp(const uint64_t& height) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
+
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
   auto get_result = mdb_get(*txn_ptr, m_block_timestamps, &key, &result);
@@ -1353,9 +1358,8 @@ uint64_t BlockchainLMDB::get_block_timestamp(const uint64_t& height) const
   else if (get_result)
     throw0(DB_ERROR("Error attempting to retrieve a timestamp from the db"));
 
-  ret = *(const uint64_t *)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
+  uint64_t ret = *(const uint64_t *)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1378,17 +1382,8 @@ size_t BlockchainLMDB::get_block_size(const uint64_t& height) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
-  size_t ret;
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
   auto get_result = mdb_get(*txn_ptr, m_block_sizes, &key, &result);
@@ -1399,9 +1394,8 @@ size_t BlockchainLMDB::get_block_size(const uint64_t& height) const
   else if (get_result)
     throw0(DB_ERROR("Error attempting to retrieve a block size from the db"));
 
-  ret = *(const size_t *)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
+  size_t ret = *(const size_t *)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1410,16 +1404,8 @@ difficulty_type BlockchainLMDB::get_block_cumulative_difficulty(const uint64_t&
   LOG_PRINT_L3("BlockchainLMDB::" << __func__ << "  height: " << height);
   check_open();
 
-  difficulty_type ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
+
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
   auto get_result = mdb_get(*txn_ptr, m_block_diffs, &key, &result);
@@ -1430,9 +1416,8 @@ difficulty_type BlockchainLMDB::get_block_cumulative_difficulty(const uint64_t&
   else if (get_result)
     throw0(DB_ERROR("Error attempting to retrieve a cumulative difficulty from the db"));
 
-  ret = *(difficulty_type*)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
+  difficulty_type ret = *(const difficulty_type*)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1458,16 +1443,7 @@ uint64_t BlockchainLMDB::get_block_already_generated_coins(const uint64_t& heigh
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
@@ -1479,9 +1455,8 @@ uint64_t BlockchainLMDB::get_block_already_generated_coins(const uint64_t& heigh
   else if (get_result)
     throw0(DB_ERROR("Error attempting to retrieve a total generated coins from the db"));
 
-  ret = *(const uint64_t*)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
+  uint64_t ret = *(const uint64_t*)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1490,16 +1465,7 @@ crypto::hash BlockchainLMDB::get_block_hash_from_height(const uint64_t& height)
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  crypto::hash ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<uint64_t> key(height);
   MDB_val result;
@@ -1512,9 +1478,8 @@ crypto::hash BlockchainLMDB::get_block_hash_from_height(const uint64_t& height)
     throw0(DB_ERROR(std::string("Error attempting to retrieve a block hash from the db: ").
           append(mdb_strerror(get_result)).c_str()));
 
-  ret = *(crypto::hash*)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
+  crypto::hash ret = *(const crypto::hash*)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1585,15 +1550,7 @@ bool BlockchainLMDB::tx_exists(const crypto::hash& h) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
@@ -1602,8 +1559,9 @@ bool BlockchainLMDB::tx_exists(const crypto::hash& h) const
   auto get_result = mdb_get(*txn_ptr, m_txs, &key, &result);
   TIME_MEASURE_FINISH(time1);
   time_tx_exists += time1;
-  if (! m_batch_active)
-    txn.commit();
+
+  TXN_POSTFIX_SUCCESS();
+
   if (get_result == MDB_NOTFOUND)
   {
     LOG_PRINT_L1("transaction with hash " << epee::string_tools::pod_to_hex(h) << " not found in db");
@@ -1620,21 +1578,18 @@ uint64_t BlockchainLMDB::get_tx_unlock_time(const crypto::hash& h) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
-  auto get_result = mdb_get(txn, m_tx_unlocks, &key, &result);
+  auto get_result = mdb_get(*txn_ptr, 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"));
 
-  ret = *(const uint64_t*)result.mv_data;
-  txn.commit();
+  uint64_t ret = *(const uint64_t*)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1643,15 +1598,7 @@ transaction BlockchainLMDB::get_tx(const crypto::hash& h) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
@@ -1667,8 +1614,8 @@ transaction BlockchainLMDB::get_tx(const crypto::hash& h) const
   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();
+
+  TXN_POSTFIX_SUCCESS();
 
   return tx;
 }
@@ -1678,15 +1625,13 @@ uint64_t BlockchainLMDB::get_tx_count() const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_stat db_stats;
-  if (mdb_stat(txn, m_txs, &db_stats))
+  if (mdb_stat(*txn_ptr, m_txs, &db_stats))
     throw0(DB_ERROR("Failed to query m_txs"));
 
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return db_stats.ms_entries;
 }
@@ -1710,16 +1655,7 @@ uint64_t BlockchainLMDB::get_tx_block_height(const crypto::hash& h) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::hash> key(h);
   MDB_val result;
@@ -1731,10 +1667,8 @@ uint64_t BlockchainLMDB::get_tx_block_height(const crypto::hash& h) const
   else if (get_result)
     throw0(DB_ERROR("DB error attempting to fetch tx height from hash"));
 
-  ret = *(const uint64_t*)result.mv_data;
-  if (! m_batch_active)
-    txn.commit();
-
+  uint64_t ret = *(const uint64_t*)result.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1743,17 +1677,16 @@ uint64_t BlockchainLMDB::get_num_outputs(const uint64_t& amount) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
-  lmdb_cur cur(txn, m_output_amounts);
+  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)
   {
+    TXN_POSTFIX_SUCCESS();
     return 0;
   }
   else if (result)
@@ -1762,7 +1695,7 @@ uint64_t BlockchainLMDB::get_num_outputs(const uint64_t& amount) const
   size_t num_elems = 0;
   mdb_cursor_count(cur, &num_elems);
 
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return num_elems;
 }
@@ -1772,21 +1705,18 @@ output_data_t BlockchainLMDB::get_output_key(const uint64_t &global_index) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  output_data_t ret;
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
-	MDB_val_copy<uint64_t> k(global_index);
+  MDB_val_copy<uint64_t> k(global_index);
   MDB_val v;
-  auto get_result = mdb_get(txn, m_output_keys, &k, &v);
+  auto get_result = mdb_get(*txn_ptr, m_output_keys, &k, &v);
   if (get_result == MDB_NOTFOUND)
     throw1(OUTPUT_DNE("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"));
-	ret = *(output_data_t *) v.mv_data;
-	txn.commit();
-	return ret;
+  output_data_t ret = *(const output_data_t *) v.mv_data;
+  TXN_POSTFIX_SUCCESS();
+  return ret;
 }
 
 output_data_t BlockchainLMDB::get_output_key(const uint64_t& amount, const uint64_t& index)
@@ -1803,16 +1733,8 @@ tx_out_index BlockchainLMDB::get_output_tx_and_index_from_global(const uint64_t&
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  tx_out_index ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-  }
+  TXN_PREFIX_RDONLY();
+
   MDB_val_copy<uint64_t> k(index);
   MDB_val v;
 
@@ -1822,7 +1744,7 @@ tx_out_index BlockchainLMDB::get_output_tx_and_index_from_global(const uint64_t&
   else if (get_result)
     throw0(DB_ERROR("DB error attempting to fetch output tx hash"));
 
-  crypto::hash tx_hash = *(crypto::hash*)v.mv_data;
+  crypto::hash tx_hash = *(const crypto::hash*)v.mv_data;
 
   get_result = mdb_get(*txn_ptr, m_output_indices, &k, &v);
   if (get_result == MDB_NOTFOUND)
@@ -1830,10 +1752,8 @@ tx_out_index BlockchainLMDB::get_output_tx_and_index_from_global(const uint64_t&
   else if (get_result)
     throw0(DB_ERROR("DB error attempting to fetch output tx index"));
 
-  ret = tx_out_index(tx_hash, *(const uint64_t *)v.mv_data);
-  if (! m_batch_active)
-    txn.commit();
-
+  tx_out_index ret = tx_out_index(tx_hash, *(const uint64_t *)v.mv_data);
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -1856,11 +1776,9 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_output_indices(const crypto::hash&
   check_open();
   std::vector<uint64_t> index_vec;
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
-  lmdb_cur cur(txn, m_tx_outputs);
+  lmdb_cur cur(*txn_ptr, m_tx_outputs);
 
   MDB_val_copy<crypto::hash> k(h);
   MDB_val v;
@@ -1883,7 +1801,7 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_output_indices(const crypto::hash&
   }
 
   cur.close();
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return index_vec;
 }
@@ -1901,9 +1819,7 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_amount_output_indices(const crypto:
 
   transaction tx = get_tx(h);
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   uint64_t i = 0;
   uint64_t global_index;
@@ -1913,7 +1829,7 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_amount_output_indices(const crypto:
 
     global_index = index_vec[i];
 
-    lmdb_cur cur(txn, m_output_amounts);
+    lmdb_cur cur(*txn_ptr, m_output_amounts);
 
     MDB_val_copy<uint64_t> k(amount);
     MDB_val v;
@@ -1952,7 +1868,7 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_amount_output_indices(const crypto:
     {
       // not found
       cur.close();
-      txn.commit();
+      TXN_POSTFIX_SUCCESS();
       throw1(OUTPUT_DNE("specified output not found in db"));
     }
 
@@ -1960,7 +1876,7 @@ std::vector<uint64_t> BlockchainLMDB::get_tx_amount_output_indices(const crypto:
     ++i;
   }
 
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return index_vec2;
 }
@@ -1972,19 +1888,17 @@ bool BlockchainLMDB::has_key_image(const crypto::key_image& img) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<crypto::key_image> val_key(img);
   MDB_val unused;
-  if (mdb_get(txn, m_spent_keys, &val_key, &unused) == 0)
+  if (mdb_get(*txn_ptr, m_spent_keys, &val_key, &unused) == 0)
   {
-    txn.commit();
+    TXN_POSTFIX_SUCCESS();
     return true;
   }
 
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
   return false;
 }
 
@@ -1993,15 +1907,13 @@ bool BlockchainLMDB::for_all_key_images(std::function<bool(const crypto::key_ima
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val k;
   MDB_val v;
   bool ret = true;
 
-  lmdb_cur cur(txn, m_spent_keys);
+  lmdb_cur cur(*txn_ptr, m_spent_keys);
   MDB_cursor_op op = MDB_FIRST;
   while (1)
   {
@@ -2011,7 +1923,7 @@ bool BlockchainLMDB::for_all_key_images(std::function<bool(const crypto::key_ima
       break;
     if (ret < 0)
       throw0(DB_ERROR("Failed to enumerate key images"));
-    const crypto::key_image k_image = *(crypto::key_image*)k.mv_data;
+    const crypto::key_image k_image = *(const crypto::key_image*)k.mv_data;
     if (!f(k_image)) {
       ret = false;
       break;
@@ -2019,7 +1931,7 @@ bool BlockchainLMDB::for_all_key_images(std::function<bool(const crypto::key_ima
   }
 
   cur.close();
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return ret;
 }
@@ -2029,15 +1941,13 @@ bool BlockchainLMDB::for_all_blocks(std::function<bool(uint64_t, const crypto::h
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val k;
   MDB_val v;
   bool ret = true;
 
-  lmdb_cur cur(txn, m_blocks);
+  lmdb_cur cur(*txn_ptr, m_blocks);
   MDB_cursor_op op = MDB_FIRST;
   while (1)
   {
@@ -2047,7 +1957,7 @@ bool BlockchainLMDB::for_all_blocks(std::function<bool(uint64_t, const crypto::h
       break;
     if (ret)
       throw0(DB_ERROR("Failed to enumerate blocks"));
-    uint64_t height = *(uint64_t*)k.mv_data;
+    uint64_t height = *(const uint64_t*)k.mv_data;
     blobdata bd;
     bd.assign(reinterpret_cast<char*>(v.mv_data), v.mv_size);
     block b;
@@ -2063,7 +1973,7 @@ bool BlockchainLMDB::for_all_blocks(std::function<bool(uint64_t, const crypto::h
   }
 
   cur.close();
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return ret;
 }
@@ -2073,15 +1983,13 @@ bool BlockchainLMDB::for_all_transactions(std::function<bool(const crypto::hash&
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val k;
   MDB_val v;
   bool ret = true;
 
-  lmdb_cur cur(txn, m_txs);
+  lmdb_cur cur(*txn_ptr, m_txs);
   MDB_cursor_op op = MDB_FIRST;
   while (1)
   {
@@ -2091,7 +1999,7 @@ bool BlockchainLMDB::for_all_transactions(std::function<bool(const crypto::hash&
       break;
     if (ret)
       throw0(DB_ERROR("Failed to enumerate transactions"));
-    const crypto::hash hash = *(crypto::hash*)k.mv_data;
+    const crypto::hash hash = *(const crypto::hash*)k.mv_data;
     blobdata bd;
     bd.assign(reinterpret_cast<char*>(v.mv_data), v.mv_size);
     transaction tx;
@@ -2104,7 +2012,7 @@ bool BlockchainLMDB::for_all_transactions(std::function<bool(const crypto::hash&
   }
 
   cur.close();
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return ret;
 }
@@ -2114,15 +2022,13 @@ bool BlockchainLMDB::for_all_outputs(std::function<bool(uint64_t amount, const c
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
+  TXN_PREFIX_RDONLY();
 
   MDB_val k;
   MDB_val v;
   bool ret = true;
 
-  lmdb_cur cur(txn, m_output_amounts);
+  lmdb_cur cur(*txn_ptr, m_output_amounts);
   MDB_cursor_op op = MDB_FIRST;
   while (1)
   {
@@ -2132,8 +2038,8 @@ bool BlockchainLMDB::for_all_outputs(std::function<bool(uint64_t amount, const c
       break;
     if (ret)
       throw0(DB_ERROR("Failed to enumerate outputs"));
-    uint64_t amount = *(uint64_t*)k.mv_data;
-    uint64_t global_index = *(uint64_t*)v.mv_data;
+    uint64_t amount = *(const uint64_t*)k.mv_data;
+    uint64_t global_index = *(const uint64_t*)v.mv_data;
     tx_out_index toi = get_output_tx_and_index_from_global(global_index);
     if (!f(amount, toi.first, toi.second)) {
       ret = false;
@@ -2142,7 +2048,7 @@ bool BlockchainLMDB::for_all_outputs(std::function<bool(uint64_t amount, const c
   }
 
   cur.close();
-  txn.commit();
+  TXN_POSTFIX_SUCCESS();
 
   return ret;
 }
@@ -2335,15 +2241,7 @@ void BlockchainLMDB::get_output_tx_and_index_from_global(const std::vector<uint6
 	check_open();
 	tx_out_indices.clear();
 
-	mdb_txn_safe txn;
-	mdb_txn_safe* txn_ptr = &txn;
-	if (m_batch_active)
-		txn_ptr = m_write_txn;
-	else
-	{
-		if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-	}
+	TXN_PREFIX_RDONLY();
 
 	for (const uint64_t &index : global_indices)
 	{
@@ -2356,7 +2254,7 @@ void BlockchainLMDB::get_output_tx_and_index_from_global(const std::vector<uint6
 		else if (get_result)
 			throw0(DB_ERROR("DB error attempting to fetch output tx hash"));
 
-		crypto::hash tx_hash = *(crypto::hash*) v.mv_data;
+		crypto::hash tx_hash = *(const crypto::hash*) v.mv_data;
 
 		get_result = mdb_get(*txn_ptr, m_output_indices, &k, &v);
 		if (get_result == MDB_NOTFOUND)
@@ -2368,8 +2266,7 @@ void BlockchainLMDB::get_output_tx_and_index_from_global(const std::vector<uint6
 		tx_out_indices.push_back(result);
 	}
 
-	if (!m_batch_active)
-		txn.commit();
+	TXN_POSTFIX_SUCCESS();
 }
 
 void BlockchainLMDB::get_output_global_indices(const uint64_t& amount, const std::vector<uint64_t> &offsets,
@@ -2387,15 +2284,7 @@ void BlockchainLMDB::get_output_global_indices(const uint64_t& amount, const std
 			max = index;
 	}
 
-	mdb_txn_safe txn;
-	mdb_txn_safe* txn_ptr = &txn;
-	if(m_batch_active)
-		txn_ptr = m_write_txn;
-	else
-	{
-		if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-	}
+	TXN_PREFIX_RDONLY();
 
 	lmdb_cur cur(*txn_ptr, m_output_amounts);
 
@@ -2474,8 +2363,7 @@ void BlockchainLMDB::get_output_global_indices(const uint64_t& amount, const std
 	}
 
 	cur.close();
-	if(!m_batch_active)
-		txn.commit();
+	TXN_POSTFIX_SUCCESS();
 
 	TIME_MEASURE_FINISH(txx);
 	LOG_PRINT_L3("txx: " << txx << " db1: " << t_dbmul << " db2: " << t_dbscan);
@@ -2493,15 +2381,8 @@ void BlockchainLMDB::get_output_key(const uint64_t &amount, const std::vector<ui
 
 	if (global_indices.size() > 0)
 	{
-    mdb_txn_safe txn;
-    mdb_txn_safe* txn_ptr = &txn;
-    if (m_batch_active)
-      txn_ptr = m_write_txn;
-    else
-    {
-      if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-        throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-    }
+		TXN_PREFIX_RDONLY();
+
 		for (const uint64_t &index : global_indices)
 		{
 			MDB_val_copy<uint64_t> k(index);
@@ -2513,12 +2394,11 @@ void BlockchainLMDB::get_output_key(const uint64_t &amount, const std::vector<ui
 			else if (get_result)
 				throw0(DB_ERROR("Error attempting to retrieve an output pubkey from the db"));
 
-			output_data_t data = *(output_data_t *) v.mv_data;
+			output_data_t data = *(const output_data_t *) v.mv_data;
 			outputs.push_back(data);
 		}
 
-    if (!m_batch_active)
-      txn.commit();
+		TXN_POSTFIX_SUCCESS();
 	}
 
 	TIME_MEASURE_FINISH(db3);
@@ -2548,24 +2428,14 @@ void BlockchainLMDB::set_hard_fork_starting_height(uint8_t version, uint64_t hei
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, 0, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-    txn_ptr = &txn;
-  }
+  TXN_PREFIX(0);
 
   MDB_val_copy<uint8_t> val_key(version);
   MDB_val_copy<uint64_t> val_value(height);
   if (auto result = mdb_put(*txn_ptr, m_hf_starting_heights, &val_key, &val_value, 0))
     throw1(DB_ERROR(std::string("Error adding hard fork starting height to db transaction: ").append(mdb_strerror(result)).c_str()));
 
-  if (!m_batch_active)
-    txn.commit();
+  TXN_POSTFIX_SUCCESS();
 }
 
 uint64_t BlockchainLMDB::get_hard_fork_starting_height(uint8_t version) const
@@ -2573,17 +2443,7 @@ uint64_t BlockchainLMDB::get_hard_fork_starting_height(uint8_t version) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint64_t ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-    txn_ptr = &txn;
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<uint8_t> val_key(version);
   MDB_val val_ret;
@@ -2593,9 +2453,8 @@ uint64_t BlockchainLMDB::get_hard_fork_starting_height(uint8_t version) const
   if (result)
     throw0(DB_ERROR("Error attempting to retrieve a hard fork starting height from the db"));
 
-  ret = *(const uint64_t*)val_ret.mv_data;
-  if (!m_batch_active)
-    txn.commit();
+  uint64_t ret = *(const uint64_t*)val_ret.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }
 
@@ -2604,25 +2463,14 @@ void BlockchainLMDB::set_hard_fork_version(uint64_t height, uint8_t version)
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-//LOG_PRINT_L1("BlockchainLMDB::set_hard_fork_version: batch " << m_batch_active << ", height " << height << ", version " << (int)version);
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, 0, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-    txn_ptr = &txn;
-  }
+  TXN_PREFIX(0);
 
   MDB_val_copy<uint64_t> val_key(height);
   MDB_val_copy<uint8_t> val_value(version);
   if (auto result = mdb_put(*txn_ptr, m_hf_versions, &val_key, &val_value, 0))
     throw1(DB_ERROR(std::string("Error adding hard fork version to db transaction: ").append(mdb_strerror(result)).c_str()));
 
-  if (!m_batch_active)
-    txn.commit();
+  TXN_POSTFIX_SUCCESS();
 }
 
 uint8_t BlockchainLMDB::get_hard_fork_version(uint64_t height) const
@@ -2630,17 +2478,7 @@ uint8_t BlockchainLMDB::get_hard_fork_version(uint64_t height) const
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
 
-  uint8_t ret;
-  mdb_txn_safe txn;
-  mdb_txn_safe* txn_ptr = &txn;
-  if (m_batch_active)
-    txn_ptr = m_write_txn;
-  else
-  {
-    if (auto mdb_res = mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
-      throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", mdb_res).c_str()));
-    txn_ptr = &txn;
-  }
+  TXN_PREFIX_RDONLY();
 
   MDB_val_copy<uint64_t> val_key(height);
   MDB_val val_ret;
@@ -2648,9 +2486,8 @@ uint8_t BlockchainLMDB::get_hard_fork_version(uint64_t height) const
   if (result == MDB_NOTFOUND || result)
     throw0(DB_ERROR("Error attempting to retrieve a hard fork version from the db"));
 
-  ret = *(const uint8_t*)val_ret.mv_data;
-  if (!m_batch_active)
-    txn.commit();
+  uint8_t ret = *(const uint8_t*)val_ret.mv_data;
+  TXN_POSTFIX_SUCCESS();
   return ret;
 }