blockchain: keep alternative blocks in LMDB

Alternative blocks are cleared on startup unless --keep-alt-blocks
is passed on the command line

3 files changed, 140 insertions, 93 deletions

diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index f733efb2f..f246d2f4e 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -726,9 +726,9 @@ bool Blockchain::reset_and_set_genesis_block(const block& b)
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
   m_timestamps_and_difficulties_height = 0;
-  m_alternative_chains.clear();
   invalidate_block_template_cache();
   m_db->reset();
+  m_db->drop_alt_blocks();
   m_hardfork->init();
 
   db_wtxn_guard wtxn_guard(m_db);
@@ -853,10 +853,15 @@ bool Blockchain::get_block_by_hash(const crypto::hash &h, block &blk, bool *orph
   // try to find block in alternative chain
   catch (const BLOCK_DNE& e)
   {
-    blocks_ext_by_hash::const_iterator it_alt = m_alternative_chains.find(h);
-    if (m_alternative_chains.end() != it_alt)
+    alt_block_data_t data;
+    cryptonote::blobdata blob;
+    if (m_db->get_alt_block(h, &data, &blob))
     {
-      blk = it_alt->second.bl;
+      if (!cryptonote::parse_and_validate_block_from_blob(blob, blk))
+      {
+        MERROR("Found block " << h << " in alt chain, but failed to parse it");
+        throw std::runtime_error("Found block in alt chain, but failed to parse it");
+      }
       if (orphan)
         *orphan = true;
       return true;
@@ -1014,7 +1019,7 @@ bool Blockchain::rollback_blockchain_switching(std::list<block>& original_chain,
 //------------------------------------------------------------------
 // This function attempts to switch to an alternate chain, returning
 // boolean based on success therein.
-bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::const_iterator>& alt_chain, bool discard_disconnected_chain)
+bool Blockchain::switch_to_alternative_blockchain(std::list<block_extended_info>& alt_chain, bool discard_disconnected_chain)
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
@@ -1025,7 +1030,7 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
   CHECK_AND_ASSERT_MES(alt_chain.size(), false, "switch_to_alternative_blockchain: empty chain passed");
 
   // verify that main chain has front of alt chain's parent block
-  if (!m_db->block_exists(alt_chain.front()->second.bl.prev_id))
+  if (!m_db->block_exists(alt_chain.front().bl.prev_id))
   {
     LOG_ERROR("Attempting to move to an alternate chain, but it doesn't appear to connect to the main chain!");
     return false;
@@ -1034,7 +1039,7 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
   // pop blocks from the blockchain until the top block is the parent
   // of the front block of the alt chain.
   std::list<block> disconnected_chain;
-  while (m_db->top_block_hash() != alt_chain.front()->second.bl.prev_id)
+  while (m_db->top_block_hash() != alt_chain.front().bl.prev_id)
   {
     block b = pop_block_from_blockchain();
     disconnected_chain.push_front(b);
@@ -1045,11 +1050,11 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
   //connecting new alternative chain
   for(auto alt_ch_iter = alt_chain.begin(); alt_ch_iter != alt_chain.end(); alt_ch_iter++)
   {
-    auto ch_ent = *alt_ch_iter;
+    const auto &bei = *alt_ch_iter;
     block_verification_context bvc = boost::value_initialized<block_verification_context>();
 
     // add block to main chain
-    bool r = handle_block_to_main_chain(ch_ent->second.bl, bvc);
+    bool r = handle_block_to_main_chain(bei.bl, bvc);
 
     // if adding block to main chain failed, rollback to previous state and
     // return false
@@ -1065,14 +1070,18 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
       // FIXME: Why do we keep invalid blocks around?  Possibly in case we hear
       // about them again so we can immediately dismiss them, but needs some
       // looking into.
-      add_block_as_invalid(ch_ent->second, get_block_hash(ch_ent->second.bl));
-      MERROR("The block was inserted as invalid while connecting new alternative chain, block_id: " << get_block_hash(ch_ent->second.bl));
-      m_alternative_chains.erase(*alt_ch_iter++);
+      const crypto::hash blkid = cryptonote::get_block_hash(bei.bl);
+      add_block_as_invalid(bei, blkid);
+      MERROR("The block was inserted as invalid while connecting new alternative chain, block_id: " << blkid);
+      m_db->remove_alt_block(blkid);
+      alt_ch_iter++;
 
       for(auto alt_ch_to_orph_iter = alt_ch_iter; alt_ch_to_orph_iter != alt_chain.end(); )
       {
-        add_block_as_invalid((*alt_ch_to_orph_iter)->second, (*alt_ch_to_orph_iter)->first);
-        m_alternative_chains.erase(*alt_ch_to_orph_iter++);
+        const auto &bei = *alt_ch_to_orph_iter++;
+        const crypto::hash blkid = cryptonote::get_block_hash(bei.bl);
+        add_block_as_invalid(bei, blkid);
+        m_db->remove_alt_block(blkid);
       }
       return false;
     }
@@ -1097,9 +1106,9 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
   }
 
   //removing alt_chain entries from alternative chains container
-  for (auto ch_ent: alt_chain)
+  for (const auto &bei: alt_chain)
   {
-    m_alternative_chains.erase(ch_ent);
+    m_db->remove_alt_block(cryptonote::get_block_hash(bei.bl));
   }
 
   m_hardfork->reorganize_from_chain_height(split_height);
@@ -1115,7 +1124,7 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
 //------------------------------------------------------------------
 // This function calculates the difficulty target for the block being added to
 // an alternate chain.
-difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std::list<blocks_ext_by_hash::const_iterator>& alt_chain, block_extended_info& bei) const
+difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std::list<block_extended_info>& alt_chain, block_extended_info& bei) const
 {
   if (m_fixed_difficulty)
   {
@@ -1133,7 +1142,7 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
     // Figure out start and stop offsets for main chain blocks
-    size_t main_chain_stop_offset = alt_chain.size() ? alt_chain.front()->second.height : bei.height;
+    size_t main_chain_stop_offset = alt_chain.size() ? alt_chain.front().height : bei.height;
     size_t main_chain_count = DIFFICULTY_BLOCKS_COUNT - std::min(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT), alt_chain.size());
     main_chain_count = std::min(main_chain_count, main_chain_stop_offset);
     size_t main_chain_start_offset = main_chain_stop_offset - main_chain_count;
@@ -1151,10 +1160,10 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
     // make sure we haven't accidentally grabbed too many blocks...maybe don't need this check?
     CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= DIFFICULTY_BLOCKS_COUNT, false, "Internal error, alt_chain.size()[" << alt_chain.size() << "] + vtimestampsec.size()[" << timestamps.size() << "] NOT <= DIFFICULTY_WINDOW[]" << DIFFICULTY_BLOCKS_COUNT);
 
-    for (auto it : alt_chain)
+    for (const auto &bei : alt_chain)
     {
-      timestamps.push_back(it->second.bl.timestamp);
-      cumulative_difficulties.push_back(it->second.cumulative_difficulty);
+      timestamps.push_back(bei.bl.timestamp);
+      cumulative_difficulties.push_back(bei.cumulative_difficulty);
     }
   }
   // if the alt chain is long enough for the difficulty calc, grab difficulties
@@ -1166,10 +1175,10 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
     size_t count = 0;
     size_t max_i = timestamps.size()-1;
     // get difficulties and timestamps from most recent blocks in alt chain
-    for(auto it: boost::adaptors::reverse(alt_chain))
+    for (const auto bei: boost::adaptors::reverse(alt_chain))
     {
-      timestamps[max_i - count] = it->second.bl.timestamp;
-      cumulative_difficulties[max_i - count] = it->second.cumulative_difficulty;
+      timestamps[max_i - count] = bei.bl.timestamp;
+      cumulative_difficulties[max_i - count] = bei.cumulative_difficulty;
       count++;
       if(count >= DIFFICULTY_BLOCKS_COUNT)
         break;
@@ -1390,16 +1399,17 @@ bool Blockchain::create_block_template(block& b, const crypto::hash *from_block,
     //build alternative subchain, front -> mainchain, back -> alternative head
     //block is not related with head of main chain
     //first of all - look in alternative chains container
-    auto it_prev = m_alternative_chains.find(*from_block);
+    alt_block_data_t prev_data;
+    bool parent_in_alt = m_db->get_alt_block(*from_block, &prev_data, NULL);
     bool parent_in_main = m_db->block_exists(*from_block);
-    if(it_prev == m_alternative_chains.end() && !parent_in_main)
+    if (!parent_in_alt && !parent_in_main)
     {
       MERROR("Unknown from block");
       return false;
     }
 
     //we have new block in alternative chain
-    std::list<blocks_ext_by_hash::const_iterator> alt_chain;
+    std::list<block_extended_info> alt_chain;
     block_verification_context bvc = boost::value_initialized<block_verification_context>();
     std::vector<uint64_t> timestamps;
     if (!build_alt_chain(*from_block, alt_chain, timestamps, bvc))
@@ -1414,7 +1424,7 @@ bool Blockchain::create_block_template(block& b, const crypto::hash *from_block,
     }
     else
     {
-      height = alt_chain.back()->second.height + 1;
+      height = alt_chain.back().height + 1;
     }
     b.major_version = m_hardfork->get_ideal_version(height);
     b.minor_version = m_hardfork->get_ideal_version();
@@ -1429,14 +1439,14 @@ bool Blockchain::create_block_template(block& b, const crypto::hash *from_block,
     }
     else
     {
-      median_weight = it_prev->second.block_cumulative_weight - it_prev->second.block_cumulative_weight / 20;
-      already_generated_coins = alt_chain.back()->second.already_generated_coins;
+      median_weight = prev_data.cumulative_weight - prev_data.cumulative_weight / 20;
+      already_generated_coins = alt_chain.back().already_generated_coins;
     }
 
     // FIXME: consider moving away from block_extended_info at some point
     block_extended_info bei = boost::value_initialized<block_extended_info>();
     bei.bl = b;
-    bei.height = alt_chain.size() ? it_prev->second.height + 1 : m_db->get_block_height(*from_block) + 1;
+    bei.height = alt_chain.size() ? prev_data.height + 1 : m_db->get_block_height(*from_block) + 1;
 
     diffic = get_next_difficulty_for_alternative_chain(alt_chain, bei);
   }
@@ -1615,16 +1625,25 @@ bool Blockchain::complete_timestamps_vector(uint64_t start_top_height, std::vect
   return true;
 }
 //------------------------------------------------------------------
-bool Blockchain::build_alt_chain(const crypto::hash &prev_id, std::list<blocks_ext_by_hash::const_iterator>& alt_chain, std::vector<uint64_t> &timestamps, block_verification_context& bvc) const
+bool Blockchain::build_alt_chain(const crypto::hash &prev_id, std::list<block_extended_info>& alt_chain, std::vector<uint64_t> &timestamps, block_verification_context& bvc) const
 {
     //build alternative subchain, front -> mainchain, back -> alternative head
-    blocks_ext_by_hash::const_iterator alt_it = m_alternative_chains.find(prev_id);
+    cryptonote::alt_block_data_t data;
+    cryptonote::blobdata blob;
+    bool found = m_db->get_alt_block(prev_id, &data, &blob);
     timestamps.clear();
-    while(alt_it != m_alternative_chains.end())
+    while(found)
     {
-      alt_chain.push_front(alt_it);
-      timestamps.push_back(alt_it->second.bl.timestamp);
-      alt_it = m_alternative_chains.find(alt_it->second.bl.prev_id);
+      block_extended_info bei;
+      CHECK_AND_ASSERT_MES(cryptonote::parse_and_validate_block_from_blob(blob, bei.bl), false, "Failed to parse alt block");
+      bei.height = data.height;
+      bei.block_cumulative_weight = data.cumulative_weight;
+      bei.cumulative_difficulty = data.cumulative_difficulty_high;
+      bei.cumulative_difficulty = (bei.cumulative_difficulty << 64) + data.cumulative_difficulty_low;
+      bei.already_generated_coins = data.already_generated_coins;
+      timestamps.push_back(bei.bl.timestamp);
+      alt_chain.push_front(std::move(bei));
+      found = m_db->get_alt_block(bei.bl.prev_id, &data, &blob);
     }
 
     // if block to be added connects to known blocks that aren't part of the
@@ -1632,20 +1651,20 @@ bool Blockchain::build_alt_chain(const crypto::hash &prev_id, std::list<blocks_e
     if(!alt_chain.empty())
     {
       // make sure alt chain doesn't somehow start past the end of the main chain
-      CHECK_AND_ASSERT_MES(m_db->height() > alt_chain.front()->second.height, false, "main blockchain wrong height");
+      CHECK_AND_ASSERT_MES(m_db->height() > alt_chain.front().height, false, "main blockchain wrong height");
 
       // make sure that the blockchain contains the block that should connect
       // this alternate chain with it.
-      if (!m_db->block_exists(alt_chain.front()->second.bl.prev_id))
+      if (!m_db->block_exists(alt_chain.front().bl.prev_id))
       {
         MERROR("alternate chain does not appear to connect to main chain...");
         return false;
       }
 
       // make sure block connects correctly to the main chain
-      auto h = m_db->get_block_hash_from_height(alt_chain.front()->second.height - 1);
-      CHECK_AND_ASSERT_MES(h == alt_chain.front()->second.bl.prev_id, false, "alternative chain has wrong connection to main chain");
-      complete_timestamps_vector(m_db->get_block_height(alt_chain.front()->second.bl.prev_id), timestamps);
+      auto h = m_db->get_block_hash_from_height(alt_chain.front().height - 1);
+      CHECK_AND_ASSERT_MES(h == alt_chain.front().bl.prev_id, false, "alternative chain has wrong connection to main chain");
+      complete_timestamps_vector(m_db->get_block_height(alt_chain.front().bl.prev_id), timestamps);
     }
     // if block not associated with known alternate chain
     else
@@ -1700,12 +1719,13 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
 
   //block is not related with head of main chain
   //first of all - look in alternative chains container
-  auto it_prev = m_alternative_chains.find(b.prev_id);
+  alt_block_data_t prev_data;
+  bool parent_in_alt = m_db->get_alt_block(b.prev_id, &prev_data, NULL);
   bool parent_in_main = m_db->block_exists(b.prev_id);
-  if(it_prev != m_alternative_chains.end() || parent_in_main)
+  if (parent_in_alt || parent_in_main)
   {
     //we have new block in alternative chain
-    std::list<blocks_ext_by_hash::const_iterator> alt_chain;
+    std::list<block_extended_info> alt_chain;
     std::vector<uint64_t> timestamps;
     if (!build_alt_chain(b.prev_id, alt_chain, timestamps, bvc))
       return false;
@@ -1713,10 +1733,10 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
     // FIXME: consider moving away from block_extended_info at some point
     block_extended_info bei = boost::value_initialized<block_extended_info>();
     bei.bl = b;
-    const uint64_t prev_height = alt_chain.size() ? it_prev->second.height : m_db->get_block_height(b.prev_id);
+    const uint64_t prev_height = alt_chain.size() ? prev_data.height : m_db->get_block_height(b.prev_id);
     bei.height = prev_height + 1;
     uint64_t block_reward = get_outs_money_amount(b.miner_tx);
-    bei.already_generated_coins = block_reward + (alt_chain.size() ? it_prev->second.already_generated_coins : m_db->get_block_already_generated_coins(prev_height));
+    bei.already_generated_coins = block_reward + (alt_chain.size() ? prev_data.already_generated_coins : m_db->get_block_already_generated_coins(prev_height));
 
     // verify that the block's timestamp is within the acceptable range
     // (not earlier than the median of the last X blocks)
@@ -1760,7 +1780,8 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
     difficulty_type main_chain_cumulative_difficulty = m_db->get_block_cumulative_difficulty(m_db->height() - 1);
     if (alt_chain.size())
     {
-      bei.cumulative_difficulty = it_prev->second.cumulative_difficulty;
+      bei.cumulative_difficulty = prev_data.cumulative_difficulty_high;
+      bei.cumulative_difficulty = (bei.cumulative_difficulty << 64) + prev_data.cumulative_difficulty_low;
     }
     else
     {
@@ -1771,15 +1792,21 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
 
     // add block to alternate blocks storage,
     // as well as the current "alt chain" container
-    auto i_res = m_alternative_chains.insert(blocks_ext_by_hash::value_type(id, bei));
-    CHECK_AND_ASSERT_MES(i_res.second, false, "insertion of new alternative block returned as it already exist");
-    alt_chain.push_back(i_res.first);
+    CHECK_AND_ASSERT_MES(!m_db->get_alt_block(id, NULL, NULL), false, "insertion of new alternative block returned as it already exists");
+    cryptonote::alt_block_data_t data;
+    data.height = bei.height;
+    data.cumulative_weight = bei.block_cumulative_weight;
+    data.cumulative_difficulty_low = (bei.cumulative_difficulty & 0xffffffffffffffff).convert_to<uint64_t>();
+    data.cumulative_difficulty_high = ((bei.cumulative_difficulty >> 64) & 0xffffffffffffffff).convert_to<uint64_t>();
+    data.already_generated_coins = bei.already_generated_coins;
+    m_db->add_alt_block(id, data, cryptonote::block_to_blob(bei.bl));
+    alt_chain.push_back(bei);
 
     // FIXME: is it even possible for a checkpoint to show up not on the main chain?
     if(is_a_checkpoint)
     {
       //do reorganize!
-      MGINFO_GREEN("###### REORGANIZE on height: " << alt_chain.front()->second.height << " of " << m_db->height() - 1 << ", checkpoint is found in alternative chain on height " << bei.height);
+      MGINFO_GREEN("###### REORGANIZE on height: " << alt_chain.front().height << " of " << m_db->height() - 1 << ", checkpoint is found in alternative chain on height " << bei.height);
 
       bool r = switch_to_alternative_blockchain(alt_chain, true);
 
@@ -1791,7 +1818,7 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
     else if(main_chain_cumulative_difficulty < bei.cumulative_difficulty) //check if difficulty bigger then in main chain
     {
       //do reorganize!
-      MGINFO_GREEN("###### REORGANIZE on height: " << alt_chain.front()->second.height << " of " << m_db->height() - 1 << " with cum_difficulty " << m_db->get_block_cumulative_difficulty(m_db->height() - 1) << std::endl << " alternative blockchain size: " << alt_chain.size() << " with cum_difficulty " << bei.cumulative_difficulty);
+      MGINFO_GREEN("###### REORGANIZE on height: " << alt_chain.front().height << " of " << m_db->height() - 1 << " with cum_difficulty " << m_db->get_block_cumulative_difficulty(m_db->height() - 1) << std::endl << " alternative blockchain size: " << alt_chain.size() << " with cum_difficulty " << bei.cumulative_difficulty);
 
       bool r = switch_to_alternative_blockchain(alt_chain, false);
       if (r)
@@ -1811,7 +1838,7 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id
     //block orphaned
     bvc.m_marked_as_orphaned = true;
     MERROR_VER("Block recognized as orphaned and rejected, id = " << id << ", height " << block_height
-        << ", parent in alt " << (it_prev != m_alternative_chains.end()) << ", parent in main " << parent_in_main
+        << ", parent in alt " << parent_in_alt << ", parent in main " << parent_in_main
         << " (parent " << b.prev_id << ", current top " << get_tail_id() << ", chain height " << get_current_blockchain_height() << ")");
   }
 
@@ -1916,11 +1943,20 @@ bool Blockchain::get_alternative_blocks(std::vector<block>& blocks) const
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
-  blocks.reserve(m_alternative_chains.size());
-  for (const auto& alt_bl: m_alternative_chains)
-  {
-    blocks.push_back(alt_bl.second.bl);
-  }
+  blocks.reserve(m_db->get_alt_block_count());
+  m_db->for_all_alt_blocks([&blocks](const crypto::hash &blkid, const cryptonote::alt_block_data_t &data, const cryptonote::blobdata *blob) {
+    if (!blob)
+    {
+      MERROR("No blob, but blobs were requested");
+      return false;
+    }
+    cryptonote::block bl;
+    if (cryptonote::parse_and_validate_block_from_blob(*blob, bl))
+      blocks.push_back(std::move(bl));
+    else
+      MERROR("Failed to parse block from blob");
+    return true;
+  }, true);
   return true;
 }
 //------------------------------------------------------------------
@@ -1928,7 +1964,7 @@ size_t Blockchain::get_alternative_blocks_count() const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
-  return m_alternative_chains.size();
+  return m_db->get_alt_block_count();
 }
 //------------------------------------------------------------------
 // This function adds the output specified by <amount, i> to the result_outs container
@@ -2416,9 +2452,9 @@ bool Blockchain::have_block(const crypto::hash& id) const
     return true;
   }
 
-  if(m_alternative_chains.count(id))
+  if(m_db->get_alt_block(id, NULL, NULL))
   {
-    LOG_PRINT_L2("block " << id << " found in m_alternative_chains");
+    LOG_PRINT_L2("block " << id << " found in alternative chains");
     return true;
   }
 
@@ -4800,11 +4836,35 @@ std::list<std::pair<Blockchain::block_extended_info,std::vector<crypto::hash>>>
 {
   std::list<std::pair<Blockchain::block_extended_info,std::vector<crypto::hash>>> chains;
 
-  for (const auto &i: m_alternative_chains)
+  blocks_ext_by_hash alt_blocks;
+  alt_blocks.reserve(m_db->get_alt_block_count());
+  m_db->for_all_alt_blocks([&alt_blocks](const crypto::hash &blkid, const cryptonote::alt_block_data_t &data, const cryptonote::blobdata *blob) {
+    if (!blob)
+    {
+      MERROR("No blob, but blobs were requested");
+      return false;
+    }
+    cryptonote::block bl;
+    block_extended_info bei;
+    if (cryptonote::parse_and_validate_block_from_blob(*blob, bei.bl))
+    {
+      bei.height = data.height;
+      bei.block_cumulative_weight = data.cumulative_weight;
+      bei.cumulative_difficulty = data.cumulative_difficulty_high;
+      bei.cumulative_difficulty = (bei.cumulative_difficulty << 64) + data.cumulative_difficulty_low;
+      bei.already_generated_coins = data.already_generated_coins;
+      alt_blocks.insert(std::make_pair(cryptonote::get_block_hash(bei.bl), std::move(bei)));
+    }
+    else
+      MERROR("Failed to parse block from blob");
+    return true;
+  }, true);
+
+  for (const auto &i: alt_blocks)
   {
-    const crypto::hash &top = i.first;
+    const crypto::hash top = cryptonote::get_block_hash(i.second.bl);
     bool found = false;
-    for (const auto &j: m_alternative_chains)
+    for (const auto &j: alt_blocks)
     {
       if (j.second.bl.prev_id == top)
       {
@@ -4818,7 +4878,7 @@ std::list<std::pair<Blockchain::block_extended_info,std::vector<crypto::hash>>>
       auto h = i.second.bl.prev_id;
       chain.push_back(top);
       blocks_ext_by_hash::const_iterator prev;
-      while ((prev = m_alternative_chains.find(h)) != m_alternative_chains.end())
+      while ((prev = alt_blocks.find(h)) != alt_blocks.end())
       {
         chain.push_back(h);
         h = prev->second.bl.prev_id;
diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h
index 244e2a89a..b7d3ce79b 100644
--- a/src/cryptonote_core/blockchain.h
+++ b/src/cryptonote_core/blockchain.h
@@ -92,24 +92,13 @@ namespace cryptonote
   {
   public:
     /**
-     * @brief Now-defunct (TODO: remove) struct from in-memory blockchain
-     */
-    struct transaction_chain_entry
-    {
-      transaction tx;
-      uint64_t m_keeper_block_height;
-      size_t m_blob_size;
-      std::vector<uint64_t> m_global_output_indexes;
-    };
-
-    /**
      * @brief container for passing a block and metadata about it on the blockchain
      */
     struct block_extended_info
     {
       block   bl; //!< the block
       uint64_t height; //!< the height of the block in the blockchain
-      size_t block_cumulative_weight; //!< the weight of the block
+      uint64_t block_cumulative_weight; //!< the weight of the block
       difficulty_type cumulative_difficulty; //!< the accumulated difficulty after that block
       uint64_t already_generated_coins; //!< the total coins minted after that block
     };
@@ -1011,20 +1000,12 @@ namespace cryptonote
 #endif
 
     // TODO: evaluate whether or not each of these typedefs are left over from blockchain_storage
-    typedef std::unordered_map<crypto::hash, size_t> blocks_by_id_index;
-
-    typedef std::unordered_map<crypto::hash, transaction_chain_entry> transactions_container;
-
     typedef std::unordered_set<crypto::key_image> key_images_container;
 
     typedef std::vector<block_extended_info> blocks_container;
 
     typedef std::unordered_map<crypto::hash, block_extended_info> blocks_ext_by_hash;
 
-    typedef std::unordered_map<crypto::hash, block> blocks_by_hash;
-
-    typedef std::map<uint64_t, std::vector<std::pair<crypto::hash, size_t>>> outputs_container; //crypto::hash - tx hash, size_t - index of out in transaction
-
 
     BlockchainDB* m_db;
 
@@ -1033,7 +1014,6 @@ namespace cryptonote
     mutable epee::critical_section m_blockchain_lock; // TODO: add here reader/writer lock
 
     // main chain
-    transactions_container m_transactions;
     size_t m_current_block_cumul_weight_limit;
     size_t m_current_block_cumul_weight_median;
 
@@ -1074,9 +1054,6 @@ namespace cryptonote
     boost::thread_group m_async_pool;
     std::unique_ptr<boost::asio::io_service::work> m_async_work_idle;
 
-    // all alternative chains
-    blocks_ext_by_hash m_alternative_chains; // crypto::hash -> block_extended_info
-
     // some invalid blocks
     blocks_ext_by_hash m_invalid_blocks;     // crypto::hash -> block_extended_info
 
@@ -1183,7 +1160,7 @@ namespace cryptonote
      *
      * @return false if the reorganization fails, otherwise true
      */
-    bool switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::const_iterator>& alt_chain, bool discard_disconnected_chain);
+    bool switch_to_alternative_blockchain(std::list<block_extended_info>& alt_chain, bool discard_disconnected_chain);
 
     /**
      * @brief removes the most recent block from the blockchain
@@ -1246,7 +1223,7 @@ namespace cryptonote
      *
      * @return true on success, false otherwise
      */
-    bool build_alt_chain(const crypto::hash &prev_id, std::list<blocks_ext_by_hash::const_iterator>& alt_chain, std::vector<uint64_t> &timestamps, block_verification_context& bvc) const;
+    bool build_alt_chain(const crypto::hash &prev_id, std::list<block_extended_info>& alt_chain, std::vector<uint64_t> &timestamps, block_verification_context& bvc) const;
 
     /**
      * @brief gets the difficulty requirement for a new block on an alternate chain
@@ -1256,7 +1233,7 @@ namespace cryptonote
      *
      * @return the difficulty requirement
      */
-    difficulty_type get_next_difficulty_for_alternative_chain(const std::list<blocks_ext_by_hash::const_iterator>& alt_chain, block_extended_info& bei) const;
+    difficulty_type get_next_difficulty_for_alternative_chain(const std::list<block_extended_info>& alt_chain, block_extended_info& bei) const;
 
     /**
      * @brief sanity checks a miner transaction before validating an entire block
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index be1ea5a17..b678f3e80 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -208,6 +208,11 @@ namespace cryptonote
     "is acted upon."
   , ""
   };
+  static const command_line::arg_descriptor<bool> arg_keep_alt_blocks  = {
+    "keep-alt-blocks"
+  , "Keep alternative blocks on restart"
+  , false
+  };
 
   //-----------------------------------------------------------------------------------------------
   core::core(i_cryptonote_protocol* pprotocol):
@@ -325,6 +330,7 @@ namespace cryptonote
     command_line::add_arg(desc, arg_prune_blockchain);
     command_line::add_arg(desc, arg_reorg_notify);
     command_line::add_arg(desc, arg_block_rate_notify);
+    command_line::add_arg(desc, arg_keep_alt_blocks);
 
     miner::init_options(desc);
     BlockchainDB::init_options(desc);
@@ -456,6 +462,7 @@ namespace cryptonote
     std::string check_updates_string = command_line::get_arg(vm, arg_check_updates);
     size_t max_txpool_weight = command_line::get_arg(vm, arg_max_txpool_weight);
     bool prune_blockchain = command_line::get_arg(vm, arg_prune_blockchain);
+    bool keep_alt_blocks = command_line::get_arg(vm, arg_keep_alt_blocks);
 
     boost::filesystem::path folder(m_config_folder);
     if (m_nettype == FAKECHAIN)
@@ -671,6 +678,9 @@ namespace cryptonote
     r = m_miner.init(vm, m_nettype);
     CHECK_AND_ASSERT_MES(r, false, "Failed to initialize miner instance");
 
+    if (!keep_alt_blocks && !m_blockchain_storage.get_db().is_read_only())
+      m_blockchain_storage.get_db().drop_alt_blocks();
+
     if (prune_blockchain)
     {
       // display a message if the blockchain is not pruned yet