core: faster find_blockchain_supplement

Since this queries block heights for blocks that may or may not
exist, queries for non existing blocks would throw an exception,
and that would slow down the loop a lot. 7 seconds to go through
a 30 hash list.

Fix this by adding an optional return block height to block_exists
and using this instead. Actual errors will still throw an
exception.

This also cuts down on log exception spam.

src/blockchain_db/berkeleydb/db_bdb.cpp

@@ -1235,7 +1235,7 @@ void BlockchainBDB::unlock()
     check_open();
 }
 
-bool BlockchainBDB::block_exists(const crypto::hash& h) const
+bool BlockchainBDB::block_exists(const crypto::hash& h, uint64_t *height) const
 {
     LOG_PRINT_L3("BlockchainBDB::" << __func__);
     check_open();
@@ -1251,6 +1251,9 @@ bool BlockchainBDB::block_exists(const crypto::hash& h) const
     else if (get_result)
         throw0(DB_ERROR("DB error attempting to fetch block index from hash"));
 
+    if (height)
+      *height = get_result - 1;
+
     return true;
 }
 

src/blockchain_db/berkeleydb/db_bdb.h

@@ -250,7 +250,7 @@ public:
 
   virtual void unlock();
 
-  virtual bool block_exists(const crypto::hash& h) const;
+  virtual bool block_exists(const crypto::hash& h, uint64_t *height = NULL) const;
 
   virtual block get_block(const crypto::hash& h) const;
 

src/blockchain_db/blockchain_db.h

@@ -736,10 +736,11 @@ public:
    * @brief checks if a block exists
    *
    * @param h the hash of the requested block
+   * @param height if non NULL, returns the block's height if found
    *
    * @return true of the block exists, otherwise false
    */
-  virtual bool block_exists(const crypto::hash& h) const = 0;
+  virtual bool block_exists(const crypto::hash& h, uint64_t *height = NULL) const = 0;
 
   /**
    * @brief fetches the block with the given hash

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -1387,7 +1387,7 @@ void BlockchainLMDB::unlock()
       auto_txn.commit(); \
   } while(0)
 
-bool BlockchainLMDB::block_exists(const crypto::hash& h) const
+bool BlockchainLMDB::block_exists(const crypto::hash& h, uint64_t *height) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   check_open();
@@ -1405,7 +1405,14 @@ bool BlockchainLMDB::block_exists(const crypto::hash& h) const
   else if (get_result)
     throw0(DB_ERROR(lmdb_error("DB error attempting to fetch block index from hash", get_result).c_str()));
   else
+  {
+    if (height)
+    {
+      const blk_height *bhp = (const blk_height *)key.mv_data;
+      *height = bhp->bh_height;
+    }
     ret = true;
+  }
 
   TXN_POSTFIX_RDONLY();
   return ret;

src/blockchain_db/lmdb/db_lmdb.h

@@ -168,7 +168,7 @@ public:
 
   virtual void unlock();
 
-  virtual bool block_exists(const crypto::hash& h) const;
+  virtual bool block_exists(const crypto::hash& h, uint64_t *height = NULL) const;
 
   virtual block get_block(const crypto::hash& h) const;
 

src/cryptonote_core/blockchain.cpp

@@ -1801,12 +1801,8 @@ bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qbloc
   {
     try
     {
-      split_height = m_db->get_block_height(*bl_it);
+      if (m_db->block_exists(*bl_it, &split_height))
-      break;
+        break;
-    }
-    catch (const BLOCK_DNE& e)
-    {
-      continue;
     }
     catch (const std::exception& e)
     {

tests/unit_tests/hardfork.cpp

@@ -58,7 +58,7 @@ public:
   virtual void block_txn_stop() {}
   virtual void block_txn_abort() {}
   virtual void drop_hard_fork_info() {}
-  virtual bool block_exists(const crypto::hash& h) const { return false; }
+  virtual bool block_exists(const crypto::hash& h, uint64_t *height) const { return false; }
   virtual block get_block(const crypto::hash& h) const { return block(); }
   virtual uint64_t get_block_height(const crypto::hash& h) const { return 0; }
   virtual block_header get_block_header(const crypto::hash& h) const { return block_header(); }