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.

2 files changed, 9 insertions, 2 deletions

diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index c0cf28dda..8ad875fc8 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/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;
diff --git a/src/blockchain_db/lmdb/db_lmdb.h b/src/blockchain_db/lmdb/db_lmdb.h
index 050e9e0ae..9df4b86d1 100644
--- a/src/blockchain_db/lmdb/db_lmdb.h
+++ b/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;