Pruning

The blockchain prunes seven eighths of prunable tx data.
This saves about two thirds of the blockchain size, while
keeping the node useful as a sync source for an eighth
of the blockchain.

No other data is currently pruned.

There are three ways to prune a blockchain:

- run monerod with --prune-blockchain
- run "prune_blockchain" in the monerod console
- run the monero-blockchain-prune utility

The first two will prune in place. Due to how LMDB works, this
will not reduce the blockchain size on disk. Instead, it will
mark parts of the file as free, so that future data will use
that free space, causing the file to not grow until free space
grows scarce.

The third way will create a second database, a pruned copy of
the original one. Since this is a new file, this one will be
smaller than the original one.

Once the database is pruned, it will stay pruned as it syncs.
That is, there is no need to use --prune-blockchain again, etc.

src/blockchain_db/blockchain_db.cpp

@@ -267,7 +267,10 @@ void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
 
   for (const auto& h : boost::adaptors::reverse(blk.tx_hashes))
   {
-    txs.push_back(get_tx(h));
+    cryptonote::transaction 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));
@@ -280,7 +283,7 @@ bool BlockchainDB::is_open() const
 
 void BlockchainDB::remove_transaction(const crypto::hash& tx_hash)
 {
-  transaction tx = get_tx(tx_hash);
+  transaction tx = get_pruned_tx(tx_hash);
 
   for (const txin_v& tx_input : tx.vin)
   {
@@ -325,6 +328,17 @@ bool BlockchainDB::get_tx(const crypto::hash& h, cryptonote::transaction &tx) co
   return true;
 }
 
+bool BlockchainDB::get_pruned_tx(const crypto::hash& h, cryptonote::transaction &tx) const
+{
+  blobdata bd;
+  if (!get_pruned_tx_blob(h, bd))
+    return false;
+  if (!parse_and_validate_tx_base_from_blob(bd, tx))
+    throw DB_ERROR("Failed to parse transaction base from blob retrieved from the db");
+
+  return true;
+}
+
 transaction BlockchainDB::get_tx(const crypto::hash& h) const
 {
   transaction tx;
@@ -333,6 +347,14 @@ transaction BlockchainDB::get_tx(const crypto::hash& h) const
   return tx;
 }
 
+transaction BlockchainDB::get_pruned_tx(const crypto::hash& h) const
+{
+  transaction tx;
+  if (!get_pruned_tx(h, tx))
+    throw TX_DNE(std::string("pruned tx with hash ").append(epee::string_tools::pod_to_hex(h)).append(" not found in db").c_str());
+  return tx;
+}
+
 void BlockchainDB::reset_stats()
 {
   num_calls = 0;

src/blockchain_db/blockchain_db.h

@@ -1125,6 +1125,17 @@ public:
    */
   virtual transaction get_tx(const crypto::hash& h) const;
 
+  /**
+   * @brief fetches the transaction base with the given hash
+   *
+   * If the transaction does not exist, the subclass should throw TX_DNE.
+   *
+   * @param h the hash to look for
+   *
+   * @return the transaction with the given hash
+   */
+  virtual transaction get_pruned_tx(const crypto::hash& h) const;
+
   /**
    * @brief fetches the transaction with the given hash
    *
@@ -1136,6 +1147,17 @@ public:
    */
   virtual bool get_tx(const crypto::hash& h, transaction &tx) const;
 
+  /**
+   * @brief fetches the transaction base with the given hash
+   *
+   * If the transaction does not exist, the subclass should return false.
+   *
+   * @param h the hash to look for
+   *
+   * @return true iff the transaction was found
+   */
+  virtual bool get_pruned_tx(const crypto::hash& h, transaction &tx) const;
+
   /**
    * @brief fetches the transaction blob with the given hash
    *
@@ -1164,6 +1186,21 @@ public:
    */
   virtual bool get_pruned_tx_blob(const crypto::hash& h, cryptonote::blobdata &tx) const = 0;
 
+  /**
+   * @brief fetches the prunable transaction blob with the given hash
+   *
+   * The subclass should return the prunable transaction stored which has the given
+   * hash.
+   *
+   * If the transaction does not exist, or if we do not have that prunable data,
+   * the subclass should return false.
+   *
+   * @param h the hash to look for
+   *
+   * @return true iff the transaction was found and we have its prunable data
+   */
+  virtual bool get_prunable_tx_blob(const crypto::hash& h, cryptonote::blobdata &tx) const = 0;
+
   /**
    * @brief fetches the prunable transaction hash
    *
@@ -1412,6 +1449,31 @@ public:
    */
   virtual void prune_outputs(uint64_t amount) = 0;
 
+  /**
+   * @brief get the blockchain pruning seed
+   * @return the blockchain pruning seed
+   */
+  virtual uint32_t get_blockchain_pruning_seed() const = 0;
+
+  /**
+   * @brief prunes the blockchain
+   * @param pruning_seed the seed to use, 0 for default (highly recommended)
+   * @return success iff true
+   */
+  virtual bool prune_blockchain(uint32_t pruning_seed = 0) = 0;
+
+  /**
+   * @brief prunes recent blockchain changes as needed, iff pruning is enabled
+   * @return success iff true
+   */
+  virtual bool update_pruning() = 0;
+
+  /**
+   * @brief checks pruning was done correctly, iff enabled
+   * @return success iff true
+   */
+  virtual bool check_pruning() = 0;
+
   /**
    * @brief runs a function over all txpool transactions
    *

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -35,6 +35,7 @@
 #include "string_tools.h"
 #include "file_io_utils.h"
 #include "common/util.h"
+#include "common/pruning.h"
 #include "cryptonote_basic/cryptonote_format_utils.h"
 #include "crypto/crypto.h"
 #include "profile_tools.h"
@@ -130,14 +131,20 @@ private:
   std::unique_ptr<char[]> data;
 };
 
-int compare_uint64(const MDB_val *a, const MDB_val *b)
+}
+
+namespace cryptonote
 {
-  const uint64_t va = *(const uint64_t *)a->mv_data;
-  const uint64_t vb = *(const uint64_t *)b->mv_data;
+
+int BlockchainLMDB::compare_uint64(const MDB_val *a, const MDB_val *b)
+{
+  uint64_t va, vb;
+  memcpy(&va, a->mv_data, sizeof(va));
+  memcpy(&vb, b->mv_data, sizeof(vb));
   return (va < vb) ? -1 : va > vb;
 }
 
-int compare_hash32(const MDB_val *a, const MDB_val *b)
+int BlockchainLMDB::compare_hash32(const MDB_val *a, const MDB_val *b)
 {
   uint32_t *va = (uint32_t*) a->mv_data;
   uint32_t *vb = (uint32_t*) b->mv_data;
@@ -151,13 +158,18 @@ int compare_hash32(const MDB_val *a, const MDB_val *b)
   return 0;
 }
 
-int compare_string(const MDB_val *a, const MDB_val *b)
+int BlockchainLMDB::compare_string(const MDB_val *a, const MDB_val *b)
 {
   const char *va = (const char*) a->mv_data;
   const char *vb = (const char*) b->mv_data;
   return strcmp(va, vb);
 }
 
+}
+
+namespace
+{
+
 /* DB schema:
  *
  * Table            Key          Data
@@ -169,6 +181,7 @@ int compare_string(const MDB_val *a, const MDB_val *b)
  * txs_pruned       txn ID       pruned txn blob
  * txs_prunable     txn ID       prunable txn blob
  * txs_prunable_hash txn ID      prunable txn hash
+ * txs_prunable_tip txn ID       height
  * tx_indices       txn hash     {txn ID, metadata}
  * tx_outputs       txn ID       [txn amount output indices]
  *
@@ -196,6 +209,7 @@ const char* const LMDB_TXS = "txs";
 const char* const LMDB_TXS_PRUNED = "txs_pruned";
 const char* const LMDB_TXS_PRUNABLE = "txs_prunable";
 const char* const LMDB_TXS_PRUNABLE_HASH = "txs_prunable_hash";
+const char* const LMDB_TXS_PRUNABLE_TIP = "txs_prunable_tip";
 const char* const LMDB_TX_INDICES = "tx_indices";
 const char* const LMDB_TX_OUTPUTS = "tx_outputs";
 
@@ -279,11 +293,6 @@ typedef struct blk_height {
     uint64_t bh_height;
 } blk_height;
 
-typedef struct txindex {
-    crypto::hash key;
-    tx_data_t data;
-} txindex;
-
 typedef struct pre_rct_outkey {
     uint64_t amount_index;
     uint64_t output_id;
@@ -549,18 +558,18 @@ bool BlockchainLMDB::need_resize(uint64_t threshold_size) const
   // additional size needed.
   uint64_t size_used = mst.ms_psize * mei.me_last_pgno;
 
-  LOG_PRINT_L1("DB map size:     " << mei.me_mapsize);
-  LOG_PRINT_L1("Space used:      " << size_used);
-  LOG_PRINT_L1("Space remaining: " << mei.me_mapsize - size_used);
-  LOG_PRINT_L1("Size threshold:  " << threshold_size);
+  MDEBUG("DB map size:     " << mei.me_mapsize);
+  MDEBUG("Space used:      " << size_used);
+  MDEBUG("Space remaining: " << mei.me_mapsize - size_used);
+  MDEBUG("Size threshold:  " << threshold_size);
   float resize_percent = RESIZE_PERCENT;
-  LOG_PRINT_L1(boost::format("Percent used: %.04f  Percent threshold: %.04f") % ((double)size_used/mei.me_mapsize) % resize_percent);
+  MDEBUG(boost::format("Percent used: %.04f  Percent threshold: %.04f") % ((double)size_used/mei.me_mapsize) % resize_percent);
 
   if (threshold_size > 0)
   {
     if (mei.me_mapsize - size_used < threshold_size)
     {
-      LOG_PRINT_L1("Threshold met (size-based)");
+      MINFO("Threshold met (size-based)");
       return true;
     }
     else
@@ -569,7 +578,7 @@ bool BlockchainLMDB::need_resize(uint64_t threshold_size) const
 
   if ((double)size_used / mei.me_mapsize  > resize_percent)
   {
-    LOG_PRINT_L1("Threshold met (percent-based)");
+    MINFO("Threshold met (percent-based)");
     return true;
   }
   return false;
@@ -581,7 +590,7 @@ bool BlockchainLMDB::need_resize(uint64_t threshold_size) const
 void BlockchainLMDB::check_and_resize_for_batch(uint64_t batch_num_blocks, uint64_t batch_bytes)
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
-  LOG_PRINT_L1("[" << __func__ << "] " << "checking DB size");
+  MTRACE("[" << __func__ << "] " << "checking DB size");
   const uint64_t min_increase_size = 512 * (1 << 20);
   uint64_t threshold_size = 0;
   uint64_t increase_size = 0;
@@ -811,6 +820,7 @@ uint64_t BlockchainLMDB::add_transaction_data(const crypto::hash& blk_hash, cons
   CURSOR(txs_pruned)
   CURSOR(txs_prunable)
   CURSOR(txs_prunable_hash)
+  CURSOR(txs_prunable_tip)
   CURSOR(tx_indices)
 
   MDB_val_set(val_tx_id, tx_id);
@@ -858,6 +868,14 @@ uint64_t BlockchainLMDB::add_transaction_data(const crypto::hash& blk_hash, cons
   if (result)
     throw0(DB_ERROR(lmdb_error("Failed to add prunable tx blob to db transaction: ", result).c_str()));
 
+  if (get_blockchain_pruning_seed())
+  {
+    MDB_val_set(val_height, m_height);
+    result = mdb_cursor_put(m_cur_txs_prunable_tip, &val_tx_id, &val_height, 0);
+    if (result)
+      throw0(DB_ERROR(lmdb_error("Failed to add prunable tx id to db transaction: ", result).c_str()));
+  }
+
   if (tx.version > 1)
   {
     MDB_val_set(val_prunable_hash, tx_prunable_hash);
@@ -883,6 +901,7 @@ void BlockchainLMDB::remove_transaction_data(const crypto::hash& tx_hash, const
   CURSOR(txs_pruned)
   CURSOR(txs_prunable)
   CURSOR(txs_prunable_hash)
+  CURSOR(txs_prunable_tip)
   CURSOR(tx_outputs)
 
   MDB_val_set(val_h, tx_hash);
@@ -898,11 +917,25 @@ void BlockchainLMDB::remove_transaction_data(const crypto::hash& tx_hash, const
   if (result)
       throw1(DB_ERROR(lmdb_error("Failed to add removal of pruned tx to db transaction: ", result).c_str()));
 
-  if ((result = mdb_cursor_get(m_cur_txs_prunable, &val_tx_id, NULL, MDB_SET)))
+  result = mdb_cursor_get(m_cur_txs_prunable, &val_tx_id, NULL, MDB_SET);
+  if (result == 0)
+  {
+      result = mdb_cursor_del(m_cur_txs_prunable, 0);
+      if (result)
+          throw1(DB_ERROR(lmdb_error("Failed to add removal of prunable tx to db transaction: ", result).c_str()));
+  }
+  else if (result != MDB_NOTFOUND)
       throw1(DB_ERROR(lmdb_error("Failed to locate prunable tx for removal: ", result).c_str()));
-  result = mdb_cursor_del(m_cur_txs_prunable, 0);
-  if (result)
-      throw1(DB_ERROR(lmdb_error("Failed to add removal of prunable tx to db transaction: ", result).c_str()));
+
+  result = mdb_cursor_get(m_cur_txs_prunable_tip, &val_tx_id, NULL, MDB_SET);
+  if (result && result != MDB_NOTFOUND)
+      throw1(DB_ERROR(lmdb_error("Failed to locate tx id for removal: ", result).c_str()));
+  if (result == 0)
+  {
+    result = mdb_cursor_del(m_cur_txs_prunable_tip, 0);
+    if (result)
+        throw1(DB_ERROR(lmdb_error("Error adding removal of tx id to db transaction", result).c_str()));
+  }
 
   if (tx.version > 1)
   {
@@ -1308,6 +1341,7 @@ void BlockchainLMDB::open(const std::string& filename, const int db_flags)
 
   // open necessary databases, and set properties as needed
   // uses macros to avoid having to change things too many places
+  // also change blockchain_prune.cpp to match
   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_INFO, MDB_INTEGERKEY | MDB_CREATE | MDB_DUPSORT | MDB_DUPFIXED, m_block_info, "Failed to open db handle for m_block_info");
@@ -1316,7 +1350,9 @@ void BlockchainLMDB::open(const std::string& filename, const int db_flags)
   lmdb_db_open(txn, LMDB_TXS, MDB_INTEGERKEY | MDB_CREATE, m_txs, "Failed to open db handle for m_txs");
   lmdb_db_open(txn, LMDB_TXS_PRUNED, MDB_INTEGERKEY | MDB_CREATE, m_txs_pruned, "Failed to open db handle for m_txs_pruned");
   lmdb_db_open(txn, LMDB_TXS_PRUNABLE, MDB_INTEGERKEY | MDB_CREATE, m_txs_prunable, "Failed to open db handle for m_txs_prunable");
-  lmdb_db_open(txn, LMDB_TXS_PRUNABLE_HASH, MDB_INTEGERKEY | MDB_CREATE, m_txs_prunable_hash, "Failed to open db handle for m_txs_prunable_hash");
+  lmdb_db_open(txn, LMDB_TXS_PRUNABLE_HASH, MDB_INTEGERKEY | MDB_DUPSORT | MDB_DUPFIXED | MDB_CREATE, m_txs_prunable_hash, "Failed to open db handle for m_txs_prunable_hash");
+  if (!(mdb_flags & MDB_RDONLY))
+    lmdb_db_open(txn, LMDB_TXS_PRUNABLE_TIP, MDB_INTEGERKEY | MDB_DUPSORT | MDB_DUPFIXED | MDB_CREATE, m_txs_prunable_tip, "Failed to open db handle for m_txs_prunable_tip");
   lmdb_db_open(txn, LMDB_TX_INDICES, MDB_INTEGERKEY | MDB_CREATE | MDB_DUPSORT | MDB_DUPFIXED, m_tx_indices, "Failed to open db handle for m_tx_indices");
   lmdb_db_open(txn, LMDB_TX_OUTPUTS, MDB_INTEGERKEY | MDB_CREATE, m_tx_outputs, "Failed to open db handle for m_tx_outputs");
 
@@ -1344,6 +1380,10 @@ void BlockchainLMDB::open(const std::string& filename, const int db_flags)
   mdb_set_dupsort(txn, m_output_amounts, compare_uint64);
   mdb_set_dupsort(txn, m_output_txs, compare_uint64);
   mdb_set_dupsort(txn, m_block_info, compare_uint64);
+  if (!(mdb_flags & MDB_RDONLY))
+    mdb_set_dupsort(txn, m_txs_prunable_tip, compare_uint64);
+  mdb_set_compare(txn, m_txs_prunable, compare_uint64);
+  mdb_set_dupsort(txn, m_txs_prunable_hash, compare_uint64);
 
   mdb_set_compare(txn, m_txpool_meta, compare_hash32);
   mdb_set_compare(txn, m_txpool_blob, compare_hash32);
@@ -1502,6 +1542,8 @@ void BlockchainLMDB::reset()
     throw0(DB_ERROR(lmdb_error("Failed to drop m_txs_prunable: ", result).c_str()));
   if (auto result = mdb_drop(txn, m_txs_prunable_hash, 0))
     throw0(DB_ERROR(lmdb_error("Failed to drop m_txs_prunable_hash: ", result).c_str()));
+  if (auto result = mdb_drop(txn, m_txs_prunable_tip, 0))
+    throw0(DB_ERROR(lmdb_error("Failed to drop m_txs_prunable_tip: ", result).c_str()));
   if (auto result = mdb_drop(txn, m_tx_indices, 0))
     throw0(DB_ERROR(lmdb_error("Failed to drop m_tx_indices: ", result).c_str()));
   if (auto result = mdb_drop(txn, m_tx_outputs, 0))
@@ -1827,6 +1869,290 @@ cryptonote::blobdata BlockchainLMDB::get_txpool_tx_blob(const crypto::hash& txid
   return bd;
 }
 
+uint32_t BlockchainLMDB::get_blockchain_pruning_seed() const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  TXN_PREFIX_RDONLY();
+  RCURSOR(properties)
+  MDB_val_str(k, "pruning_seed");
+  MDB_val v;
+  int result = mdb_cursor_get(m_cur_properties, &k, &v, MDB_SET);
+  if (result == MDB_NOTFOUND)
+    return 0;
+  if (result)
+    throw0(DB_ERROR(lmdb_error("Failed to retrieve pruning seed: ", result).c_str()));
+  if (v.mv_size != sizeof(uint32_t))
+    throw0(DB_ERROR("Failed to retrieve or create pruning seed: unexpected value size"));
+  uint32_t pruning_seed;
+  memcpy(&pruning_seed, v.mv_data, sizeof(pruning_seed));
+  TXN_POSTFIX_RDONLY();
+  return pruning_seed;
+}
+
+static bool is_v1_tx(MDB_cursor *c_txs_pruned, MDB_val *tx_id)
+{
+  MDB_val v;
+  int ret = mdb_cursor_get(c_txs_pruned, tx_id, &v, MDB_SET);
+  if (ret)
+    throw0(DB_ERROR(lmdb_error("Failed to find transaction pruned data: ", ret).c_str()));
+  if (v.mv_size == 0)
+    throw0(DB_ERROR("Invalid transaction pruned data"));
+  return cryptonote::is_v1_tx(cryptonote::blobdata_ref{(const char*)v.mv_data, v.mv_size});
+}
+
+enum { prune_mode_prune, prune_mode_update, prune_mode_check };
+
+bool BlockchainLMDB::prune_worker(int mode, uint32_t pruning_seed)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  const uint32_t log_stripes = tools::get_pruning_log_stripes(pruning_seed);
+  if (log_stripes && log_stripes != CRYPTONOTE_PRUNING_LOG_STRIPES)
+    throw0(DB_ERROR("Pruning seed not in range"));
+  pruning_seed = tools::get_pruning_stripe(pruning_seed);;
+  if (pruning_seed > (1ul << CRYPTONOTE_PRUNING_LOG_STRIPES))
+    throw0(DB_ERROR("Pruning seed not in range"));
+  check_open();
+
+  TIME_MEASURE_START(t);
+
+  size_t n_total_records = 0, n_prunable_records = 0, n_pruned_records = 0;
+  uint64_t n_bytes = 0;
+
+  mdb_txn_safe txn;
+  auto result = mdb_txn_begin(m_env, NULL, 0, txn);
+  if (result)
+    throw0(DB_ERROR(lmdb_error("Failed to create a transaction for the db: ", result).c_str()));
+
+  MDB_stat db_stats;
+  if ((result = mdb_stat(txn, m_txs_prunable, &db_stats)))
+    throw0(DB_ERROR(lmdb_error("Failed to query m_txs_prunable: ", result).c_str()));
+  const size_t pages0 = db_stats.ms_branch_pages + db_stats.ms_leaf_pages + db_stats.ms_overflow_pages;
+
+  MDB_val_str(k, "pruning_seed");
+  MDB_val v;
+  result = mdb_get(txn, m_properties, &k, &v);
+  bool prune_tip_table = false;
+  if (result == MDB_NOTFOUND)
+  {
+    // not pruned yet
+    if (mode != prune_mode_prune)
+    {
+      txn.abort();
+      TIME_MEASURE_FINISH(t);
+      MDEBUG("Pruning not enabled, nothing to do");
+      return true;
+    }
+    if (pruning_seed == 0)
+      pruning_seed = tools::get_random_stripe();
+    pruning_seed = tools::make_pruning_seed(pruning_seed, CRYPTONOTE_PRUNING_LOG_STRIPES);
+    v.mv_data = &pruning_seed;
+    v.mv_size = sizeof(pruning_seed);
+    result = mdb_put(txn, m_properties, &k, &v, 0);
+    if (result)
+      throw0(DB_ERROR("Failed to save pruning seed"));
+    prune_tip_table = false;
+  }
+  else if (result == 0)
+  {
+    // pruned already
+    if (v.mv_size != sizeof(uint32_t))
+      throw0(DB_ERROR("Failed to retrieve or create pruning seed: unexpected value size"));
+    const uint32_t data = *(const uint32_t*)v.mv_data;
+    if (pruning_seed == 0)
+      pruning_seed = tools::get_pruning_stripe(data);
+    if (tools::get_pruning_stripe(data) != pruning_seed)
+      throw0(DB_ERROR("Blockchain already pruned with different seed"));
+    if (tools::get_pruning_log_stripes(data) != CRYPTONOTE_PRUNING_LOG_STRIPES)
+      throw0(DB_ERROR("Blockchain already pruned with different base"));
+    pruning_seed = tools::make_pruning_seed(pruning_seed, CRYPTONOTE_PRUNING_LOG_STRIPES);
+    prune_tip_table = (mode == prune_mode_update);
+  }
+  else
+  {
+    throw0(DB_ERROR(lmdb_error("Failed to retrieve or create pruning seed: ", result).c_str()));
+  }
+
+  if (mode == prune_mode_check)
+    MINFO("Checking blockchain pruning...");
+  else
+    MINFO("Pruning blockchain...");
+
+  MDB_cursor *c_txs_pruned, *c_txs_prunable, *c_txs_prunable_tip;
+  result = mdb_cursor_open(txn, m_txs_pruned, &c_txs_pruned);
+  if (result)
+    throw0(DB_ERROR(lmdb_error("Failed to open a cursor for txs_pruned: ", result).c_str()));
+  result = mdb_cursor_open(txn, m_txs_prunable, &c_txs_prunable);
+  if (result)
+    throw0(DB_ERROR(lmdb_error("Failed to open a cursor for txs_prunable: ", result).c_str()));
+  result = mdb_cursor_open(txn, m_txs_prunable_tip, &c_txs_prunable_tip);
+  if (result)
+    throw0(DB_ERROR(lmdb_error("Failed to open a cursor for txs_prunable_tip: ", result).c_str()));
+  const uint64_t blockchain_height = height();
+
+  if (prune_tip_table)
+  {
+    MDB_cursor_op op = MDB_FIRST;
+    while (1)
+    {
+      int ret = mdb_cursor_get(c_txs_prunable_tip, &k, &v, op);
+      op = MDB_NEXT;
+      if (ret == MDB_NOTFOUND)
+        break;
+      if (ret)
+        throw0(DB_ERROR(lmdb_error("Failed to enumerate transactions: ", ret).c_str()));
+
+      uint64_t block_height;
+      memcpy(&block_height, v.mv_data, sizeof(block_height));
+      if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS < blockchain_height)
+      {
+        ++n_total_records;
+        if (!tools::has_unpruned_block(block_height, blockchain_height, pruning_seed) && !is_v1_tx(c_txs_pruned, &k))
+        {
+          ++n_prunable_records;
+          result = mdb_cursor_get(c_txs_prunable, &k, &v, MDB_SET);
+          if (result == MDB_NOTFOUND)
+            MWARNING("Already pruned at height " << block_height << "/" << blockchain_height);
+          else if (result)
+            throw0(DB_ERROR(lmdb_error("Failed to find transaction prunable data: ", result).c_str()));
+          else
+          {
+            MDEBUG("Pruning at height " << block_height << "/" << blockchain_height);
+            ++n_pruned_records;
+            n_bytes += k.mv_size + v.mv_size;
+            result = mdb_cursor_del(c_txs_prunable, 0);
+            if (result)
+              throw0(DB_ERROR(lmdb_error("Failed to delete transaction prunable data: ", result).c_str()));
+          }
+        }
+        result = mdb_cursor_del(c_txs_prunable_tip, 0);
+        if (result)
+          throw0(DB_ERROR(lmdb_error("Failed to delete transaction tip data: ", result).c_str()));
+      }
+    }
+  }
+  else
+  {
+    MDB_cursor *c_tx_indices;
+    result = mdb_cursor_open(txn, m_tx_indices, &c_tx_indices);
+    if (result)
+      throw0(DB_ERROR(lmdb_error("Failed to open a cursor for tx_indices: ", result).c_str()));
+    MDB_cursor_op op = MDB_FIRST;
+    while (1)
+    {
+      int ret = mdb_cursor_get(c_tx_indices, &k, &v, op);
+      op = MDB_NEXT;
+      if (ret == MDB_NOTFOUND)
+        break;
+      if (ret)
+        throw0(DB_ERROR(lmdb_error("Failed to enumerate transactions: ", ret).c_str()));
+
+      ++n_total_records;
+      //const txindex *ti = (const txindex *)v.mv_data;
+      txindex ti;
+      memcpy(&ti, v.mv_data, sizeof(ti));
+      const uint64_t block_height = ti.data.block_id;
+      if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
+      {
+        MDB_val_set(kp, ti.data.tx_id);
+        MDB_val_set(vp, block_height);
+        if (mode == prune_mode_check)
+        {
+          result = mdb_cursor_get(c_txs_prunable_tip, &kp, &vp, MDB_SET);
+          if (result && result != MDB_NOTFOUND)
+            throw0(DB_ERROR(lmdb_error("Error looking for transaction prunable data: ", result).c_str()));
+          if (result == MDB_NOTFOUND)
+            MERROR("Transaction not found in prunable tip table for height " << block_height << "/" << blockchain_height <<
+                ", seed " << epee::string_tools::to_string_hex(pruning_seed));
+        }
+        else
+        {
+          result = mdb_cursor_put(c_txs_prunable_tip, &kp, &vp, 0);
+          if (result && result != MDB_NOTFOUND)
+            throw0(DB_ERROR(lmdb_error("Error looking for transaction prunable data: ", result).c_str()));
+        }
+      }
+      MDB_val_set(kp, ti.data.tx_id);
+      if (!tools::has_unpruned_block(block_height, blockchain_height, pruning_seed) && !is_v1_tx(c_txs_pruned, &kp))
+      {
+        result = mdb_cursor_get(c_txs_prunable, &kp, &v, MDB_SET);
+        if (result && result != MDB_NOTFOUND)
+          throw0(DB_ERROR(lmdb_error("Error looking for transaction prunable data: ", result).c_str()));
+        if (mode == prune_mode_check)
+        {
+          if (result != MDB_NOTFOUND)
+            MERROR("Prunable data found for pruned height " << block_height << "/" << blockchain_height <<
+                ", seed " << epee::string_tools::to_string_hex(pruning_seed));
+        }
+        else
+        {
+          ++n_prunable_records;
+          if (result == MDB_NOTFOUND)
+            MWARNING("Already pruned at height " << block_height << "/" << blockchain_height);
+          else
+          {
+            MDEBUG("Pruning at height " << block_height << "/" << blockchain_height);
+            ++n_pruned_records;
+            n_bytes += kp.mv_size + v.mv_size;
+            result = mdb_cursor_del(c_txs_prunable, 0);
+            if (result)
+              throw0(DB_ERROR(lmdb_error("Failed to delete transaction prunable data: ", result).c_str()));
+          }
+        }
+      }
+      else
+      {
+        if (mode == prune_mode_check)
+        {
+          MDB_val_set(kp, ti.data.tx_id);
+          result = mdb_cursor_get(c_txs_prunable, &kp, &v, MDB_SET);
+          if (result && result != MDB_NOTFOUND)
+            throw0(DB_ERROR(lmdb_error("Error looking for transaction prunable data: ", result).c_str()));
+          if (result == MDB_NOTFOUND)
+            MERROR("Prunable data not found for unpruned height " << block_height << "/" << blockchain_height <<
+                ", seed " << epee::string_tools::to_string_hex(pruning_seed));
+        }
+      }
+    }
+    mdb_cursor_close(c_tx_indices);
+  }
+
+  if ((result = mdb_stat(txn, m_txs_prunable, &db_stats)))
+    throw0(DB_ERROR(lmdb_error("Failed to query m_txs_prunable: ", result).c_str()));
+  const size_t pages1 = db_stats.ms_branch_pages + db_stats.ms_leaf_pages + db_stats.ms_overflow_pages;
+  const size_t db_bytes = (pages0 - pages1) * db_stats.ms_psize;
+
+  mdb_cursor_close(c_txs_prunable_tip);
+  mdb_cursor_close(c_txs_prunable);
+  mdb_cursor_close(c_txs_pruned);
+
+  txn.commit();
+
+  TIME_MEASURE_FINISH(t);
+
+  MINFO((mode == prune_mode_check ? "Checked" : "Pruned") << " blockchain in " <<
+      t << " ms: " << (n_bytes/1024.0f/1024.0f) << " MB (" << db_bytes/1024.0f/1024.0f << " MB) pruned in " <<
+      n_pruned_records << " records (" << pages0 - pages1 << "/" << pages0 << " " << db_stats.ms_psize << " byte pages), " <<
+      n_prunable_records << "/" << n_total_records << " pruned records");
+  return true;
+}
+
+bool BlockchainLMDB::prune_blockchain(uint32_t pruning_seed)
+{
+  return prune_worker(prune_mode_prune, pruning_seed);
+}
+
+bool BlockchainLMDB::update_pruning()
+{
+  return prune_worker(prune_mode_update, 0);
+}
+
+bool BlockchainLMDB::check_pruning()
+{
+  return prune_worker(prune_mode_check, 0);
+}
+
 bool BlockchainLMDB::for_all_txpool_txes(std::function<bool(const crypto::hash&, const txpool_tx_meta_t&, const cryptonote::blobdata*)> f, bool include_blob, bool include_unrelayed_txes) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
@@ -2428,6 +2754,36 @@ bool BlockchainLMDB::get_pruned_tx_blob(const crypto::hash& h, cryptonote::blobd
   return true;
 }
 
+bool BlockchainLMDB::get_prunable_tx_blob(const crypto::hash& h, cryptonote::blobdata &bd) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  TXN_PREFIX_RDONLY();
+  RCURSOR(tx_indices);
+  RCURSOR(txs_prunable);
+
+  MDB_val_set(v, h);
+  MDB_val result;
+  auto get_result = mdb_cursor_get(m_cur_tx_indices, (MDB_val *)&zerokval, &v, MDB_GET_BOTH);
+  if (get_result == 0)
+  {
+    const txindex *tip = (const txindex *)v.mv_data;
+    MDB_val_set(val_tx_id, tip->data.tx_id);
+    get_result = mdb_cursor_get(m_cur_txs_prunable, &val_tx_id, &result, MDB_SET);
+  }
+  if (get_result == MDB_NOTFOUND)
+    return false;
+  else if (get_result)
+    throw0(DB_ERROR(lmdb_error("DB error attempting to fetch tx from hash", get_result).c_str()));
+
+  bd.assign(reinterpret_cast<char*>(result.mv_data), result.mv_size);
+
+  TXN_POSTFIX_RDONLY();
+
+  return true;
+}
+
 bool BlockchainLMDB::get_prunable_tx_hash(const crypto::hash& tx_hash, crypto::hash &prunable_hash) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);

src/blockchain_db/lmdb/db_lmdb.h

@@ -40,6 +40,11 @@
 namespace cryptonote
 {
 
+typedef struct txindex {
+    crypto::hash key;
+    tx_data_t data;
+} txindex;
+
 typedef struct mdb_txn_cursors
 {
   MDB_cursor *m_txc_blocks;
@@ -53,6 +58,7 @@ typedef struct mdb_txn_cursors
   MDB_cursor *m_txc_txs_pruned;
   MDB_cursor *m_txc_txs_prunable;
   MDB_cursor *m_txc_txs_prunable_hash;
+  MDB_cursor *m_txc_txs_prunable_tip;
   MDB_cursor *m_txc_tx_indices;
   MDB_cursor *m_txc_tx_outputs;
 
@@ -62,6 +68,8 @@ typedef struct mdb_txn_cursors
   MDB_cursor *m_txc_txpool_blob;
 
   MDB_cursor *m_txc_hf_versions;
+
+  MDB_cursor *m_txc_properties;
 } mdb_txn_cursors;
 
 #define m_cur_blocks	m_cursors->m_txc_blocks
@@ -73,12 +81,14 @@ typedef struct mdb_txn_cursors
 #define m_cur_txs_pruned	m_cursors->m_txc_txs_pruned
 #define m_cur_txs_prunable	m_cursors->m_txc_txs_prunable
 #define m_cur_txs_prunable_hash	m_cursors->m_txc_txs_prunable_hash
+#define m_cur_txs_prunable_tip	m_cursors->m_txc_txs_prunable_tip
 #define m_cur_tx_indices	m_cursors->m_txc_tx_indices
 #define m_cur_tx_outputs	m_cursors->m_txc_tx_outputs
 #define m_cur_spent_keys	m_cursors->m_txc_spent_keys
 #define m_cur_txpool_meta	m_cursors->m_txc_txpool_meta
 #define m_cur_txpool_blob	m_cursors->m_txc_txpool_blob
 #define m_cur_hf_versions	m_cursors->m_txc_hf_versions
+#define m_cur_properties	m_cursors->m_txc_properties
 
 typedef struct mdb_rflags
 {
@@ -92,12 +102,14 @@ typedef struct mdb_rflags
   bool m_rf_txs_pruned;
   bool m_rf_txs_prunable;
   bool m_rf_txs_prunable_hash;
+  bool m_rf_txs_prunable_tip;
   bool m_rf_tx_indices;
   bool m_rf_tx_outputs;
   bool m_rf_spent_keys;
   bool m_rf_txpool_meta;
   bool m_rf_txpool_blob;
   bool m_rf_hf_versions;
+  bool m_rf_properties;
 } mdb_rflags;
 
 typedef struct mdb_threadinfo
@@ -232,6 +244,7 @@ public:
 
   virtual bool get_tx_blob(const crypto::hash& h, cryptonote::blobdata &tx) const;
   virtual bool get_pruned_tx_blob(const crypto::hash& h, cryptonote::blobdata &tx) const;
+  virtual bool get_prunable_tx_blob(const crypto::hash& h, cryptonote::blobdata &tx) const;
   virtual bool get_prunable_tx_hash(const crypto::hash& tx_hash, crypto::hash &prunable_hash) const;
 
   virtual uint64_t get_tx_count() const;
@@ -264,6 +277,11 @@ public:
   virtual bool get_txpool_tx_meta(const crypto::hash& txid, txpool_tx_meta_t &meta) const;
   virtual bool get_txpool_tx_blob(const crypto::hash& txid, cryptonote::blobdata &bd) const;
   virtual cryptonote::blobdata get_txpool_tx_blob(const crypto::hash& txid) const;
+  virtual uint32_t get_blockchain_pruning_seed() const;
+  virtual bool prune_blockchain(uint32_t pruning_seed = 0);
+  virtual bool update_pruning();
+  virtual bool check_pruning();
+
   virtual bool for_all_txpool_txes(std::function<bool(const crypto::hash&, const txpool_tx_meta_t&, const cryptonote::blobdata*)> f, bool include_blob = false, bool include_unrelayed_txes = true) const;
 
   virtual bool for_all_key_images(std::function<bool(const crypto::key_image&)>) const;
@@ -309,6 +327,11 @@ public:
 
   bool get_output_distribution(uint64_t amount, uint64_t from_height, uint64_t to_height, std::vector<uint64_t> &distribution, uint64_t &base) const;
 
+  // helper functions
+  static int compare_uint64(const MDB_val *a, const MDB_val *b);
+  static int compare_hash32(const MDB_val *a, const MDB_val *b);
+  static int compare_string(const MDB_val *a, const MDB_val *b);
+
 private:
   void do_resize(uint64_t size_increase=0);
 
@@ -361,6 +384,8 @@ private:
 
   inline void check_open() const;
 
+  bool prune_worker(int mode, uint32_t pruning_seed);
+
   virtual bool is_read_only() const;
 
   virtual uint64_t get_database_size() const;
@@ -393,6 +418,7 @@ private:
   MDB_dbi m_txs_pruned;
   MDB_dbi m_txs_prunable;
   MDB_dbi m_txs_prunable_hash;
+  MDB_dbi m_txs_prunable_tip;
   MDB_dbi m_tx_indices;
   MDB_dbi m_tx_outputs;