Blockchain: option for fast manual block popping

src/blockchain_db/blockchain_db.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -172,13 +172,6 @@ void BlockchainDB::init_options(boost::program_options::options_description& des
   command_line::add_arg(desc, arg_db_salvage);
 }
 
-void BlockchainDB::pop_block()
-{
-  block blk;
-  std::vector<transaction> txs;
-  pop_block(blk, txs);
-}
-
 void BlockchainDB::add_transaction(const crypto::hash& blk_hash, const transaction& tx, const epee::span<const std::uint8_t> blob, const crypto::hash* tx_hash_ptr, const crypto::hash* tx_prunable_hash_ptr)
 {
   bool miner_tx = false;
@@ -311,7 +304,7 @@ void BlockchainDB::set_hard_fork(HardFork* hf)
   m_hardfork = hf;
 }
 
-void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
+void BlockchainDB::pop_block(block& blk, std::vector<transaction>* txs)
 {
   blk = get_top_block();
 
@@ -319,10 +312,13 @@ void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
 
   for (const auto& h : boost::adaptors::reverse(blk.tx_hashes))
   {
-    cryptonote::transaction tx;
+    if (txs)
-    if (!get_tx(h, tx) && !get_pruned_tx(h, tx))
+    {
-      throw DB_ERROR("Failed to get pruned or unpruned transaction from the db");
+      cryptonote::transaction tx;
-    txs.push_back(std::move(tx));
+      if (!get_tx(h, tx) && !get_pruned_tx(h, tx))
+        throw DB_ERROR("Failed to get pruned or unpruned transaction from the db");
+      txs->push_back(std::move(tx));
+    }
     remove_transaction(h);
   }
   remove_transaction(get_transaction_hash(blk.miner_tx));
@@ -481,8 +477,9 @@ void BlockchainDB::fixup()
       if (!has_key_image(ki))
       {
         LOG_PRINT_L1("Fixup: detected missing key images from block 202612! Popping blocks...");
+        block blk;
         while (height() > 202612)
-          pop_block();
+          pop_block(blk, /*txs=*/nullptr);
       }
     }
   }

src/blockchain_db/blockchain_db.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 //
 // All rights reserved.
 //
@@ -538,13 +538,6 @@ private:
   /*********************************************************************
    * private concrete members
    *********************************************************************/
-  /**
-   * @brief private version of pop_block, for undoing if an add_block fails
-   *
-   * This function simply calls pop_block(block& blk, std::vector<transaction>& txs)
-   * with dummy parameters, as the returns-by-reference can be discarded.
-   */
-  void pop_block();
 
   // helper function to remove transaction from blockchain
   /**
@@ -1151,13 +1144,12 @@ public:
    * implements remove_* functions.
    *
    * The subclass should return by reference the popped block and
-   * its associated transactions
+   * its associated transactions, if applicable to that overload
    *
-   * @param blk return-by-reference the block which was popped
+   * @param[out] blk the block which was popped
-   * @param txs return-by-reference the transactions from the popped block
+   * @param[out] txs the non-coinbase transactions from the popped block (optional)
    */
-  virtual void pop_block(block& blk, std::vector<transaction>& txs);
+  virtual void pop_block(block& blk, std::vector<transaction>* txs);
-
 
   /**
    * @brief check if a transaction with a given hash exists

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without modification, are
@@ -4157,7 +4157,7 @@ uint64_t BlockchainLMDB::add_block(const std::pair<block, blobdata>& blk, size_t
   return ++m_height;
 }
 
-void BlockchainLMDB::pop_block(block& blk, std::vector<transaction>& txs)
+void BlockchainLMDB::pop_block(block& blk, std::vector<transaction>* txs)
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();

src/blockchain_db/lmdb/db_lmdb.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without modification, are
@@ -342,7 +342,7 @@ public:
 
   bool block_rtxn_start(MDB_txn **mtxn, mdb_txn_cursors **mcur) const;
 
-  void pop_block(block& blk, std::vector<transaction>& txs) override;
+  void pop_block(block& blk, std::vector<transaction>* txs) override;
 
   bool can_thread_bulk_indices() const override { return true; }
 

src/blockchain_utilities/blockchain_import.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 //
 // All rights reserved.
 //
@@ -100,11 +100,10 @@ int pop_blocks(cryptonote::core& core, int num_blocks)
 
   int quit = 0;
   block popped_block;
-  std::vector<transaction> popped_txs;
   for (int i=0; i < num_blocks; ++i)
   {
     // simple_core.m_storage.pop_block_from_blockchain() is private, so call directly through db
-    core.get_blockchain_storage().get_db().pop_block(popped_block, popped_txs);
+    core.get_blockchain_storage().get_db().pop_block(popped_block, /*txs=*/nullptr);
     quit = 1;
   }
 

src/cryptonote_core/blockchain.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 //
 // All rights reserved.
 //
@@ -408,10 +408,9 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline
         MGINFO("Popping blocks... " << top_height);
       ++num_popped_blocks;
       block popped_block;
-      std::vector<transaction> popped_txs;
       try
       {
-        m_db->pop_block(popped_block, popped_txs);
+        m_db->pop_block(popped_block, /*txs=*/nullptr);
       }
       // anything that could cause this to throw is likely catastrophic,
       // so we re-throw
@@ -548,7 +547,7 @@ bool Blockchain::deinit()
 //------------------------------------------------------------------
 // This function removes blocks from the top of blockchain.
 // It starts a batch and calls private method pop_block_from_blockchain().
-void Blockchain::pop_blocks(uint64_t nblocks)
+void Blockchain::pop_blocks(uint64_t nblocks, const bool keep_txs)
 {
   uint64_t i = 0;
   CRITICAL_REGION_LOCAL(m_tx_pool);
@@ -563,7 +562,7 @@ void Blockchain::pop_blocks(uint64_t nblocks)
       nblocks = std::min(nblocks, blockchain_height - 1);
     while (i < nblocks && !m_cancel.load())
     {
-      pop_block_from_blockchain();
+      pop_block_from_blockchain(keep_txs);
       ++i;
     }
   }
@@ -588,9 +587,9 @@ void Blockchain::pop_blocks(uint64_t nblocks)
 }
 //------------------------------------------------------------------
 // This function tells BlockchainDB to remove the top block from the
-// blockchain and then returns all transactions (except the miner tx, of course)
+// blockchain and then, if keep_txs is true, returns all transactions
-// from it to the tx_pool
+// (except the miner tx, of course) from it to the tx_pool
-block Blockchain::pop_block_from_blockchain()
+block Blockchain::pop_block_from_blockchain(bool keep_txs)
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
@@ -606,7 +605,7 @@ block Blockchain::pop_block_from_blockchain()
   const uint8_t previous_hf_version = get_current_hard_fork_version();
   try
   {
-    m_db->pop_block(popped_block, popped_txs);
+    m_db->pop_block(popped_block, keep_txs ? &popped_txs : nullptr);
   }
   // anything that could cause this to throw is likely catastrophic,
   // so we re-throw
@@ -626,7 +625,7 @@ block Blockchain::pop_block_from_blockchain()
 
   // return transactions from popped block to the tx_pool
   size_t pruned = 0;
-  for (transaction& tx : popped_txs)
+  if (keep_txs) for (transaction& tx : popped_txs)
   {
     if (tx.pruned)
     {
@@ -1117,7 +1116,7 @@ bool Blockchain::rollback_blockchain_switching(std::list<block>& original_chain,
   // remove blocks from blockchain until we get back to where we should be.
   while (m_db->height() != rollback_height)
   {
-    pop_block_from_blockchain();
+    pop_block_from_blockchain(/*keep_txs=*/true);
   }
   CHECK_AND_ASSERT_THROW_MES(update_next_cumulative_weight_limit(), "Error updating next cumulative weight limit");
 
@@ -1167,7 +1166,7 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<block_extended_info>
   std::list<block> disconnected_chain;
   while (m_db->top_block_hash() != alt_chain.front().bl.prev_id)
   {
-    block b = pop_block_from_blockchain();
+    block b = pop_block_from_blockchain(/*keep_txs=*/true);
     disconnected_chain.push_front(b);
   }
   CHECK_AND_ASSERT_THROW_MES(update_next_cumulative_weight_limit(), "Error updating next cumulative weight limit");
@@ -4342,7 +4341,7 @@ leave:
   if (!update_next_cumulative_weight_limit())
   {
     MERROR("Failed to update next cumulative weight limit");
-    pop_block_from_blockchain();
+    pop_block_from_blockchain(/*keep_txs=*/true);
     return false;
   }
 

src/cryptonote_core/blockchain.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 //
 // All rights reserved.
 //
@@ -1131,8 +1131,9 @@ namespace cryptonote
      * @brief removes blocks from the top of the blockchain
      *
      * @param nblocks number of blocks to be removed
+     * @param keep_txs whether to place popped non-coinbase transactions back into the mempool
      */
-    void pop_blocks(uint64_t nblocks);
+    void pop_blocks(uint64_t nblocks, bool keep_txs);
 
     /**
      * @brief checks whether a given block height is included in the precompiled block hash area
@@ -1377,9 +1378,11 @@ namespace cryptonote
     /**
      * @brief removes the most recent block from the blockchain
      *
+     * @param keep_txs whether to place popped non-coinbase transactions back into the mempool
+     *
      * @return the block removed
      */
-    block pop_block_from_blockchain();
+    block pop_block_from_blockchain(bool keep_txs);
 
     /**
      * @brief validate and add a new block to the end of the blockchain

src/daemon/command_parser_executor.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -931,9 +931,14 @@ bool t_command_parser_executor::sync_info(const std::vector<std::string>& args)
 
 bool t_command_parser_executor::pop_blocks(const std::vector<std::string>& args)
 {
-  if (args.size() != 1)
+  if (args.size() < 1)
   {
-    std::cout << "Invalid syntax: One parameter expected. For more details, use the help command." << std::endl;
+    std::cout << "Invalid syntax: At least one parameter expected. For more details, use the help command." << std::endl;
+    return true;
+  }
+  else if (args.size() > 2)
+  {
+    std::cout << "Invalid syntax: A maximum of two parameters expected. For more details, use the help command." << std::endl;
     return true;
   }
 
@@ -945,7 +950,22 @@ bool t_command_parser_executor::pop_blocks(const std::vector<std::string>& args)
       std::cout << "Invalid syntax: Number of blocks must be greater than 0. For more details, use the help command." << std::endl;
       return true;
     }
-    return m_executor.pop_blocks(nblocks);
+    bool keep_txs = false;
+    if (args.size() > 1)
+    {
+      const std::string keep_arg = args.at(1);
+      if (keep_arg == "keep-txs")
+        keep_txs = true;
+      else if (keep_arg == "no-keep-txs")
+        keep_txs = false;
+      else
+      {
+        std::cout << "Invalid syntax: Unrecognized argument: '" << keep_arg
+          << "'. For more details, use the help command." << std::endl;
+        return true;
+      }
+    }
+    return m_executor.pop_blocks(nblocks, keep_txs);
   }
   catch (const boost::bad_lexical_cast&)
   {

src/daemon/command_server.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -299,8 +299,8 @@ t_command_server::t_command_server(
     m_command_lookup.set_handler(
       "pop_blocks"
     , std::bind(&t_command_parser_executor::pop_blocks, &m_parser, p::_1)
-    , "pop_blocks <nblocks>"
+    , "pop_blocks <nblocks> [keep-txs|no-keep-txs]"
-    , "Remove blocks from end of blockchain"
+    , "Remove blocks from end of blockchain, optionally moving popped txs into the mempool (not default)"
     );
     m_command_lookup.set_handler(
       "version"

src/daemon/rpc_command_executor.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -2310,13 +2310,14 @@ bool t_rpc_command_executor::sync_info()
     return true;
 }
 
-bool t_rpc_command_executor::pop_blocks(uint64_t num_blocks)
+bool t_rpc_command_executor::pop_blocks(uint64_t num_blocks, bool keep_txs)
 {
   cryptonote::COMMAND_RPC_POP_BLOCKS::request req;
   cryptonote::COMMAND_RPC_POP_BLOCKS::response res;
   std::string fail_message = "pop_blocks failed";
 
   req.nblocks = num_blocks;
+  req.keep_txs = keep_txs;
   if (m_is_rpc)
   {
     if (!m_rpc_client->rpc_request(req, res, "/pop_blocks", fail_message.c_str()))

src/daemon/rpc_command_executor.h

@@ -6,7 +6,7 @@
 
 */
 
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -154,7 +154,7 @@ public:
 
   bool sync_info();
 
-  bool pop_blocks(uint64_t num_blocks);
+  bool pop_blocks(uint64_t num_blocks, bool keep_txs);
 
   bool prune_blockchain();
 

src/rpc/core_rpc_server.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -3174,7 +3174,7 @@ namespace cryptonote
   {
     RPC_TRACKER(pop_blocks);
 
-    m_core.get_blockchain_storage().pop_blocks(req.nblocks);
+    m_core.get_blockchain_storage().pop_blocks(req.nblocks, req.keep_txs);
 
     res.height = m_core.get_current_blockchain_height();
     res.status = CORE_RPC_STATUS_OK;

src/rpc/core_rpc_server_commands_defs.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -101,7 +101,7 @@ inline const std::string get_rpc_status(const bool trusted_daemon, const std::st
 // advance which version they will stop working with
 // Don't go over 32767 for any of these
 #define CORE_RPC_VERSION_MAJOR 3
-#define CORE_RPC_VERSION_MINOR 17
+#define CORE_RPC_VERSION_MINOR 18
 #define MAKE_CORE_RPC_VERSION(major,minor) (((major)<<16)|(minor))
 #define CORE_RPC_VERSION MAKE_CORE_RPC_VERSION(CORE_RPC_VERSION_MAJOR, CORE_RPC_VERSION_MINOR)
 
@@ -2498,10 +2498,12 @@ inline const std::string get_rpc_status(const bool trusted_daemon, const std::st
     struct request_t: public rpc_request_base
     {
       uint64_t nblocks;
+      bool keep_txs;
 
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE_PARENT(rpc_request_base)
         KV_SERIALIZE(nblocks)
+        KV_SERIALIZE_OPT(keep_txs, true)
       END_KV_SERIALIZE_MAP()
     };
     typedef epee::misc_utils::struct_init<request_t> request;

tests/block_weight/block_weight.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2019-2024, The Monero Project
+// Copyright (c) 2019-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -96,7 +96,7 @@ public:
       *block_height = h - 1;
     return top;
   }
-  virtual void pop_block(cryptonote::block &blk, std::vector<cryptonote::transaction> &txs) override { blocks.pop_back(); }
+  virtual void pop_block(cryptonote::block &, std::vector<cryptonote::transaction> *) override { blocks.pop_back(); }
   virtual void set_hard_fork_version(uint64_t height, uint8_t version) override { if (height >= hf.size()) hf.resize(height + 1); hf[height] = version; }
   virtual uint8_t get_hard_fork_version(uint64_t height) const override { if (height >= hf.size()) return 255; return hf[height]; }
 

tests/core_tests/chaingen.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2024, The Monero Project
+// Copyright (c) 2014-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -132,7 +132,7 @@ namespace
       return blocks[blocks.size()-1].bl;
     }
 
-    virtual void pop_block(cryptonote::block &blk, std::vector<cryptonote::transaction> &txs) override { if (!blocks.empty()) blocks.pop_back(); }
+    virtual void pop_block(cryptonote::block &, std::vector<cryptonote::transaction> *) override { if (!blocks.empty()) blocks.pop_back(); }
     virtual void set_hard_fork_version(uint64_t height, uint8_t version) override { if (height >= hf.size()) hf.resize(height + 1); hf[height] = version; }
     virtual uint8_t get_hard_fork_version(uint64_t height) const override { if (height >= hf.size()) return 255; return hf[height]; }
 

tests/unit_tests/long_term_block_weight.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2019-2024, The Monero Project
+// Copyright (c) 2019-2026, The Monero Project
 // 
 // All rights reserved.
 // 
@@ -90,7 +90,7 @@ public:
       *block_height = h - 1;
     return top;
   }
-  virtual void pop_block(cryptonote::block &blk, std::vector<cryptonote::transaction> &txs) override { blocks.pop_back(); }
+  virtual void pop_block(cryptonote::block &blk, std::vector<cryptonote::transaction> *txs) override { blocks.pop_back(); }
 
 private:
   std::vector<block_t> blocks;
@@ -206,9 +206,8 @@ TEST(long_term_block_weight, multi_pop)
   }
 
   cryptonote::block b;
-  std::vector<cryptonote::transaction> txs;
   for (uint64_t h = 0; h < num_pop; ++h)
-    bc->get_db().pop_block(b, txs);
+    bc->get_db().pop_block(b, /*txs=*/nullptr);
   ASSERT_TRUE(bc->update_next_cumulative_weight_limit());
 
   ASSERT_EQ(effective_median, bc->get_current_cumulative_block_weight_median());
@@ -267,8 +266,7 @@ TEST(long_term_block_weight, pop_invariant_max)
     for (int i = 0; i < remove; ++i)
     {
       cryptonote::block b;
-      std::vector<cryptonote::transaction> txs;
+      bc->get_db().pop_block(b, /*txs=*/nullptr);
-      bc->get_db().pop_block(b, txs);
       ASSERT_TRUE(bc->update_next_cumulative_weight_limit());
     }
     for (int i = 0; i < add; ++i)
@@ -317,8 +315,7 @@ TEST(long_term_block_weight, pop_invariant_random)
     for (int i = 0; i < remove; ++i)
     {
       cryptonote::block b;
-      std::vector<cryptonote::transaction> txs;
+      bc->get_db().pop_block(b, /*txs=*/nullptr);
-      bc->get_db().pop_block(b, txs);
       ASSERT_TRUE(bc->update_next_cumulative_weight_limit());
       const uint64_t effective_median = bc->get_current_cumulative_block_weight_median();
       const uint64_t effective_limit = bc->get_current_cumulative_block_weight_limit();